I started off with McMaster Carr, my favorite one stop shop for the discerning mechanical or manufacturing engineer. I'm waiting on an order right now, with a press button incremental hinge, an adjustable friction hinge, and a lever lock hinge.
But another great way to get some inspiration is by heading to your local hardware store, or even your local outdoors/camping store. We found a slot hinge used for folding a chair which was something I had considered. Only problem is our structure is not very large, and these act like a brace in the corners so it can take up quite a bit of room.
We also found a rounded hinge that was used for a camping table and the spring wire/slotted structures that you usually see on pop up tents.
My favorite find, however, was the radial hinge from a jogging stroller. If you can picture the collapsible top of a stroller with rounded supports that allows it to fold close almost like an accordion you can see where this radial hinge fits in.
There's something to be said for looking to the latest research or the most new and advanced manufacturing techniques but there's also an advantage to checking out basic consumer products that are already out there and seeing where inspiration strikes. You never know what simple mechanism did not occur to you in your hunt to optimize your design. Of course, this might be a bit too simplified if you're dealing with a failed water pump or something a bit more complex but if you're thinking for a prototype don't be afraid to stop by your local hardware store just to browse. You never know what you'll see.