Sounds in Peep are stored in raw PCM signed-16 bit CD quality (44100 kHz,
stereo) format. Oh yeah, and they're little endian too 
If that sounds
scary, fear not. If you're on a machine whose byte order is like Intel's,
just load up your CD quality waves (They should be at 44100 Khz) and convert
them to .snd format. Then just rename the sound files according the servers
convention and you're all set.
To play a sound under GNU/Linux, you can do:
$ bplay -s 44100 -b 16 -S 
bplay can be retrieved from its homepage at: http:://www.amberdata.demon.co.uk/bplay.
Alternatively, if your distribution comes with the GNU/Linux "play" utility, you can play a sound file with:
$ play -c 2 -t raw -r 44100 -size=w -f s
Unfortunately, there is no direct support for .wav's at the moment but hopefully that will be added in the future. In the meantime, many tools can convert to .snd format and so you need not worry. Support for .mp3s in the future is iffy. Although it would greatly compress the sound packages, it also brings a large computational overhead (decoding). I want peepd to be able to run on older machines without performance issues. However, .mp3 might become an alternative in the future. If anyone is interested in adding support for different sound formats, please email me: mgilfix@eecs.tufts.edu.