When I’m doing UI or graphic design (the latter of which is always a struggle), I often get stuck designing things over and over again in the same way simply from lack of creativity, or I find it impossible to get things to look “right” and I can’t figure out why. When this happens, I like to check out other people’s work to get ideas and inspiration. Here is a list I’ve compiled of websites that I bookmark and come back to in these situations.

This site is relatively new, so there isn’t a ton of content yet but it looks like it has amazing potential.
Here at the Icon Deposit, we give you the opportunity to post your icons, designs, codes, and screenshots to promote your work and gain new clients. We feature hundreds of free icons, icon sets, UI/UX design, illustrator graphics, vector art, code tutorials for CSS, CSS3, JQuery, photoshop tutorials and tons more.

Similar to Icon Deposit, this is a sort of mash of ux.stackexchange.com with screenshots and image galleries but without free graphics. The community of users is exclusive in that you need to be invited to be a member, or have a GitHub account. In this way, they are able to control the content quality a little bit more.

Pattern Tap has organized sets of screenshots in user-defined categories, which is really useful when you want to search by a specific UI element (eg. navigation, 404 pages with white guys throwing gang signs, etc.)

CSS Remix kind of Pattern Tap but with full-page screenshots, and none of the content is organized, sorted or searchable in any way.

Dribbble is show and tell for designers. Players share shots—small screenshots of the designs and applications they are working on… Some have called Dribbble “Twitter for designers.” Shots are to Dribbble as tweets are to Twitter.
Enjoy! And if you know of any more similar sites, I’d love to know.