I found these samples using http://www.findsounds.com. Here are the URLs
for them:

Beep:
http://www.parabox.or.jp/~comet/wav/CHIN.WAV

Channel join/leave:
http://newton.tamuk.edu/~suson/entertainment/sounds/wav/Effects/DoorOpening.wav
http://newton.tamuk.edu/~suson/entertainment/sounds/wav/Effects/DoorClosing.wav

Chatline:
http://www6.shizuokanet.ne.jp/~miya/WAVE/hasami.wav
http://clio.mit.csu.edu.au/~mkavakli/int-films/bivers/animations/click.wav

Pawel Stolowski