Another free kw tool I like (I'm biased, it's my app) is "keyword gadget". It's a very simple but useful overture tool. You type in multiple keywords and it fetches multiple overture popularity lists -- compiling them into one. I keep getting frustrated with WordTracker and coming back to "the gadget".
If you'd like to try, it's here (tiny, no install req) :
http://acme-web-design.info/keyword-research-gadget.htm
- chad