Been playing a few systems and liked Shadowrun a lot. Mostly because of the cyberpunk setting and the insane things you could get done. I have played online using IRC too. Was rather simple since there are dice-scripts in the internet. Only downside was, that it took really long since typing takes much more time than actually saying things. But with a combination of irc/ts (using irc to roll the dice and keep track of what is happening and TS to actually play) this should work out rather fine.
Getting a chatroom and a script is easy to achieve. Just chose some random irc-server like quakenet or rizon and create a channel. Get people in there and register it (even though registering will not be needed I suppose). Then start playing