First I grabbed the latest, uncrippled ffmpeg, following this howto http://ubuntuforums.org/showthread.php?t=786095
now after some experimenting I settled on the following params to convert to a format the phone supported.
ffmpeg -i input_file -acodec libfaac -ar 22000 -ab 32k -ac 2 -vtag mp4v -r 15 -s 320x240 output_file.mp4then I drop the output_file.mp4 onto the phone's miniSD card, in the folder "Videos", and I'm done.