Try searching the freeware section of snapfiles.com
. I've found a lot of cool (and free!) programs there. Hope that helps.
Thanks for the tip. I found a solution: Xnview (http://www.xnview.com
) has a nice command line tool NConvert. Many human readable options, 400 different formats supported. Freeware for personal use. No nags, no limits, not crippled. Works fine. I build a batch with 3 lines to do the job.