Warning: Bash scripting follows in this message. If this confuses/baffles you, stop reading here. 
QUOTE(heshamwhwaf @ Sat May 5 2007, 17:58) [snapback]390556[/snapback]
... to be able to set custom sounds based on who I'm chatting with or who signs in or calls. It would be a nice feature to have, and as you guys expressed an interest in adding features just for us Linux users, please let me know what you guys think.
Well, today is your lucky day, because I actually felt similarly, and implemented a feature just for you (and me

).
If you go into the Options dialog and Notifications, choose the event (such as Sign In, Incoming Call or Incoming Chat Message) and then choose Advanced, you will see a rather undocumented feature called "Execute the following script:"
The are a number of funky things you can do with this feature, but for now, try setting a script in this box like:
~/.Skype/soundscript.sh %type %sskype
Then, create a file called ~/.Skype/soundscript.sh which contains something like the following:
-- snip --
CODE
#!/bin/sh
if [ "$1" == "ContactOnline" ]; then
if [ "$2" == "bill" ]; then
aplay /usr/share/skype/sounds/custom/contacts/bill.wav
elif [ "$2" == "charlotte" ]; then
aplay /usr/share/skype/sounds/custom/contacts/wolfwhistle.wav
else
aplay /usr/share/skype/sounds/ContactOnline.wav
fi
elif [ "$1" == "ChatIncoming" ]; then
if [ "$2" == "sandra" ]; then
aplay /usr/share/skype/sounds/custom/chat/sandra.wav
else
aplay /usr/share/skype/sounds/ChatIncoming.wav
fi
fi
-- snip --
Hopefully, that made some sense

If not, then ignore it. If so, then enjoy it

It's up to you if you want to set this as a 'global' script (ie. one that gets executed on all events), or a local script to the event. At the moment, there is a possibility that global scripts aren't yet functional, as I'm not sure where we were up to with this implementation before the alpha release. But sound-specific scripts are definitely functioning

Enjoy!
Andypoo.