I know there are tons of these out there, but I just found this one and I really like it. I was reading Library Stuff and Steven's of … which lead to to the list of top links from del.icio.us … when I saw a link to the HTML Color Code Combination Chooser.
What a fun little tool! Give it a whirl. While you're at it you can try one of these color tools:
We used the last one of these to help us pick colors for our new Intranet.