Soo… we all know about ColourLovers and ColorMod… but do you know about ColorBlender 
It’s not a new site, but it’s on that I haven’t seen here and I thought I’d toss the knowledge of this wonderful site along. You pick a color it matches colors that look good w/ your primary… then it lets you download them in PS, act format or AI, eps format so you can put them in your swatches palette. One of the best features that it provides IMO is that it matches your color w/ the closest Pantone.
It’s fantasitical.
http://colorblender.com/
