For video your options are:
iChatAV to iChatAV, to AIM 5.9 (PC) or Trillian (PC) (Audio and Video)
Yahoo Beta (Mac) to Yahoo (MAC) (PC) Video, no audio
aMSN (Mac)to aMSN (Mac) or aMSN (Mac) to MSN (PC) Video only, no Audio
Mercury (Mac) to Mercury (Mac) or Mercury (Mac) to MSN (PC) Video Only, no Audio
Skype Beta (Mac) to Skype Beta (Mac) or Skype Beta to Skype (PC) (Audio & Video)
MSN (Mac) and Adium (Mac) do not support Video or Audio
Most of the above programs can be found at
http://www.versiontracker.com
I hope this is what you were looking for!