If you're Amiga-based, take a look at the credits on Eric Schwartz's Animated Amiga Tribute - he lists the software used.
If you're on Mac/Windows and serious about animation, check out Bauhaus Mirage (an evolution of our TVPaint) at
http://www.bauhaussoftware.com/If you have a Mac, you could also try the legendary LivingCels, made by Creature House (an awesome little software company bought up by Microsoft and utterly FUBAR, rather like Blue Ribbon Soundworks). The software can be freely downloaded for Mac (but not Windows); a download link, documentation and sample movies are available at
http://www.livingcels.comIncidentally, the links page at livingcels.com points to some other interesting and innovative animation software.