The Samsung Exclaim™ requires the 3g2 format for its ringtones or even videos. This is a format that is optimized for 3G phones. Fortunately on Linux, FFmpeg is a very complete tool to work with audio and video formats and convert between them, and it can, of course, generate 3g2 files.
If you have compiled and installed the right packages (Medibuntu repository with the libaac support, for example), you can easily do one of these commands with ffmpeg:
Convert Audio (mp3) to 3g2
ffmpeg -i test.mp3 -acodec libfaac -ab 64k -ar 22050 test.3g2
You can tweak this command and use other audio file formats as well.
Convert Video (avi) to 3g2
ffmpeg -i test.mpg -acodec libfaac -ab 64k -ar 22050 -vcodec mpeg4 -s qcif -b 120k -r 30 out.3g2
It also works with other video file formats. You'll certainly need to tweak this command to get a better quality.
How to use them
To select a 3g2 as a custom ringtone, just go to the ringer/ringtone menu as usual, and choose Videos, then From Memory Card, and that's where you can pick your 3g2's.
Make sure your ringtone is smaller than 500Kb and 30 seconds to be sure it works fine.