Feel free to contribute more links.
A number of links can already be found in the Related Fetishes section.
If a page is in a language you don't understand, you can try Google translate to get a rough idea what the text is about. (Of course text in images is not translated.)

My polls on MisterPoll

At Mister Poll (http://original.misterpoll.com) there are a number of polls on overalls, shortalls, dungarees, etc. I've added several:
What overalls do you own?
Why and how do you wear overalls?
Describe your dream overalls
Stuck in clothing
Interestingly enough, without any question or hint from my side, several people answered in the dream overalls poll in a free text area that they wanted their overalls locking. So I added a additional poll on that: Your locking dream overalls
And a number of polls that are not directly about overalls, but some related subjects:
Clothes the wearer can't take off him/herself
Did you wet / soil your clothing because they were stuck?
Dressing a man in female clothes? (women only)
Discomfort for Fashion
Diapered and/or babified with restraints
Religious or cultural restraints
Would you buy a chastity belt? and its sister poll What if: chastity belt on sale locally (Unluckily these seem to be lost now)
And of course my poll asking your opinions on the earlier Ariel galleries.

And some other interesting message threads (on polls not by me):
Back zip clothing, Yes/No, Why?
Shortalls - also take a look at the message threads.
You can find all my MisterPoll polls and messages on my public profile.

Overalls sites

The Overalls Forum in English.
Latzhosen-Forum (or the old location Latzhosen-Forum), an active German overalls forum.
Petra's Bibboys, mostly boys, but also a gallery with girls.
a Japanese overalls site (just follow the links and you'll find pictures, partly of the guy showing off his collection, but also of women/girls/boys)

Picture collections

Flickr: womens in overalls
Flickr: The Overalls Project - Women
There is an Italian guy who likes to be stuck by his (?) overalls straps. Currently his alias is OverallsDecay, and he has accounts on e.g. DeviantArt and Instagram. On his DeviantArt profile he has a nice collection of overalls and bondage photo's in his favorites. He used to have a Flickr account under the name Marilpet.
Motherless gallery of Denimlover15, with his wife in her hotpant dungarees and bondage
Peter Pools modifies pictures to suggest restrictive clothing, in particular with hoodies. Some of them are jumpsuits/rompers. Take a look at his Flickr account.
Alex is mad about collars, and sometimes his models wear overalls or skirtalls. He has a profile on fetlife as AlexK and on flickr as AlexCollarCollection. (You might need an account for either.) See for instance flickr pic1, flickr pic2 or fetlife pic3.
Steve-jones-the-2nd has a set of Sexy Escape Challenges on DeviantArt (although they look more like girls struggling in bondage than actual escapes) with animated GIF's. There are three of a girl in shortalls: Overalls 1, Overalls 2, and Overals 3. (You probably need a DeviantArt account to see these.)

Blogs

leather overalls and coveralls (Not updated anymore)
Rubber, Overalls, and Bondage has many rubber, bondage and feminization pictures, but overalls not so many lately. Searching the blog for overalls will show the older ones easily, though. (Not updated anymore)
Women in Overalls by Overalls_Lover, Arizona. (Not updated anymore)
Overoles by ElOverol, both in Spanish and English. (Not updated anymore)
Art Foster is into tight and restricting clothing, and draws and writes about it. He has a DeviantArt page, and moderates a group there called Confining Clothing. (He used to run the yahoo group with the same name, but Yahoo is severely shackling the groups.)

Bondage Shops with interesting Clothing

A swiss online shop, o.g. style sells clothes with special pockets, where the hands of the wearer can be invisibly secured with buckle straps. (Page is in German, but just scroll down to the 'Handfixierung in der Tasche'.)
A online shop in Pakistan offers straight-overalls: Kubind Canvas Strait Trouser.
There is also a shop supplying for adult babies, called Privatina, with interesting and locking clothes, but they asked me to remove my link to them (no idea why they don't want me to advertise for them). So just search for the shop's name in your favorite search engine and I'm sure you'll find it.
The Etsy store StraitjacketShop not only sells straitjackets, but also diaper covers, optionally with shoulder straps, mittens, booties, etc. They also have an orange prison jumpsuit with back zip and buckled leather collar. Chastity belt maker FancySteel also makes bondage video's, and in their latest series, Chastity prison 4, they use that jumpsuit with a locking collar. On their Instagram account there is a preview.

Commercial bondage sites

Amateur Bondage has a number of bondage video's that feature women in overalls. Go to their store and check out video's 21, 28 (overalls and overall dress), 42 (locking dress) 88, 92, 145 (only kidnapper in overalls), 210 (undressing while handcuffed in the back), 215 and 305. The store also has a few video's of 'bound in ski suit' (not from Amateur Bondage).
My Bondage Girl is about German girl Anja who also has several bondage video's in which she wears overalls: 'Anja testet Kerzenwachs und Klammern', 'Anja´s neue Latzhose', 'Latzhosengirl', Latzhosengirl (1), 'Straightjackets and Bags', 'Die Versicherungsvertreterin 2' parts 3 and 4 and Anja's selfbondage 2. In Anja's collection you can find quick shortcuts to the movies. There are several screenshots in Gallery 4. (Site not updated in over 2 years now.)
German Chastity Forum - a set of Forums about Chastity and related subjects. Especially in the "Stories zu Medizinischen Fesseln" there are some stories about locking jumpsuits etc.: look for the contributions of Lord Grey (esp. Sabine Furst: now translated and found here at the contributor's section), and Ovvan. That is, if you can understand German.
In the Infernal Restraints video April Showers Bronte wears shortalls for the first third of the video, until they are cut off from her. (How dare they!) There is a screenshot in Gallery 4.
A Czech site on tickling, with a girl in leather cuffs and stocks
Girl Asylum is a site that deals with straitjackets, armbinders, mittens, and such. They have one video and photo series of Mayke in shortalls and Posey Mitts (scroll down).
Girls in Steel offers a 2 part photo series of 2 girls playing with metal bondage, one of whom wears denim shortalls: part 1 and part 2.
Consensual Bondage also offers a photo series and video of 2 girls playing with leather, chains and padlocks, one of whom wears denim shortalls: the photo set, and the video.

Video collections

BondageSM.org has several photo sets of models in overalls with mostly cuffs and tape: Maya in front-buttoning denim overalls, Olivia in a denim jumpsuit, Molly in leather shortalls, Brianna in leather overalls dress, Lauren in Pikachu onesie, Ella in leather overalls dress. I haven't bought any set; if you do let me know how you like them.

Another site that has a lot of interesting material is Clips4sale.com; they even have Overalls as a category.
JeansBound has a collection of girls bound in jeans overalls.
If you like suspension in overalls, take a look at Torvea Customs, who has several clips at Clips4sale that contain girls stuck hanging from their overalls straps. (Note that the model is actually hanging from a harness under her overalls, as you can spot in a hanging wedgie video. Overalls are not normally suitable for suspension!). Another one is Ginarys Kinky Adventures.
For overalls and diapers you can take a look at Adriana.
And if you're into chastity, you should definitely check out Wendy Warrior. (no overalls there though, but some locked zentai suits)
Mistress Nicci's Fetish Theater has several overalls video's; take a special look at the Overalls Club: 5 ladies in an overalls club suspend one of them for a hazing.

Pornhub also has large fetish photo and video collections, some of the interesting ones: An Overall Predicament, Anja Overalls, Misuzu Cuffs, Bound Overalls.
(Note that most video's there will probably violate copyrights, so if that bothers you, it would be best not to sponsor them by your visits.)

For the gunge lovers, Jayce Lane's House of Mess has a number of video's with overalls.

Of course YouTube has the largest video collection, and although they try to ban fetish materials, there are still some interesting finds there, like this Asian video of girl in front-buttoned denim overalls tied to a chair.
Here is a song parodying love for (childish) overalls: an ode to her overalls (adult baby)
Here is an wrestling match (similar to All-star Pro), where both girls on one team are in overalls. One of them gets tied with tape, pulled on her overalls straps, etc.: ChocoProLIVE! #63 "I Quit Match". (Note that you can find more ChocoProLive video's with Lulupencil and Emipencil in their overalls)