Wannathis - 3d illustrations and freebies
UI Flow Cards - Construct web pages with ease, using cards
Craftwork - A collection of User Interface resources made by Craftwork
The User Interview Exchange - Give a user interview, get a user interview - It's all free
Icons8 - Free app for Mac & Windows already containing 39,800 icons. Allows to search and import icons…
Humaaans - Mix-&-match illustrations of humans with a design library.