Skype Screen Sharing Is A Huge (And Free) Productivity Tool
techcrunch.com
techcrunch.com
Any competing tool (or set of tools) would have to accomplish those same goals.
Also, I tend to use skype (or email) whenever I have to paste a large block of text (like a stack trace), since Yahoo and AIM both avoid sending messages if they're too long.
http://lifehacker.com/5453124/skype-21-beta-2-puts-screen-sh...
The way it should work is that when you log into Skype on your computer and you have an active call it says something like "you have a call going on another device, would you like to join it on this computer?" and then you could screenshare.
Skype uses a form of UDP hole punching to get through NAT/firewall issues and connect two users directly. Unless AIM has this as well (again, not sure), you'll probably have much better luck getting Skype screen sharing to connect.