1. Paletton: http://paletton.com Color scheme designer. Fiddle around with different color schemes. Great for art projects, scrapbooking, web design; it even gives you the hex codes for the colors.
2. LOLTrek: http://granades.com/2007/05/02/loltrek/ The "Tribbles" episode of Star Trek in lolspeak.
3. Rinkworks: http://www.rinkworks.com/ About as old-school as you can get on the web, but still lots of fun. Book In A Minute, text-based games, puzzles, the Fantasy Novelist's Exam, fantasy name generator, horror stories from tech support, everything you need to kill an hour or three.
4. Wordle: http://www.wordle.net/ Create word cloud graphics.
5. Madglibs: http://www.madglibs.com/index.php Online mad libs games.
Have fun out there!
[blog note: at the moment, a number of my blog post categories aren't working right. I hope to have this fixed soon.]