64 is a good one to use. That's still used a lot on Kaillera.
There is a newer version of Kaillera that a lot of people are using these days. It's P2P Kaillera and it can be downloaded here:
http://kaillera.movsq.net/
There is a file called kaillera.dll in your MAME directory. That file is Kaillera. It controls all the internet play stuff for MAME.
This replaces it with a new Kaillera.dll that lets you either connect to a server the way regular kaillera works or connect straight to an opponent by entering their IP address.
Hopefully some folks will get back to you about playing on Kaillera.
THere is a "Who's On?" box on the left side of the website. That's something that lets you advertise to members if you want to play Kaillera.
Pick the game you want to play and the service you want to play on (for instance Kaillera) and then enter something in the text box. If you are on AIM and are looking for a match put "AIM:your user" in the box and then hit the checkbox next to it.
That way everyone can see you want to play.
Also, be sure to fill in your AIM name or whatever in your profile. That way others can add you when they see this post and message you when they feel like playing.
If I am on a real computer later I'll try to hop on Kaillera too.