Whenever I need project inspiration I check out this site. They have a huge searchable catalog of design concepts. Although not all of them are practical and most aren`t even related to robots at all, after browsing the site for 10 minutes I`ve got a brain full of ideas.
My second port of call when looking for inspiration would be deviantart. Some really good stuff here too but you`ve got to sift through a lot of crap to find it.