Addendum to myself:
http://www.coolorus.com/ for Photoshop or as a Flash standalone. It's more of a color-picker tool (based off of CorelDRAW's), but it has a schemer feature built-in.
Right? I was incredibly surprised that there aren't others like it (Kuler angers me for reasons I will not get into here). Colourlovers has ColorSchemer (http://www.colorschemer.com/osx_info.php) but I'm not a fan of the interface or the price tag.
http://www.colourlovers.com/
http://colllor.com/
http://tools.medialab.sciences-po.fr/iwanthue/
http://www.eigenlogik.com/spectrum/ (OS X 10.7+ app)