Finding good, free software usually leads to a twenty minute Google search that routes me to dead ends (aka shareware).
To solve this problem, a few months back I started using a combination of the Google reader search function and a site called Cool OS X Apps (a great blog that features different OS X software daily - which is often freeware) to perform filtered searches which lead to actual downloads.
Check out this screencast to see this method in action.
*I am sure there are other Mac and Windows blogs out there that would work just as well, I just haven’t found them (please post to comments if you know of any).