If you're talking about NITDroid ( The Android port to N900 ) it dosen't yet support even voice calls fully , the camera dosen't work with NITDroid so that's a sure no . But i've not tried VOIP apps like Skype or any other.

If you're talking about Maemo , we have Skype which works like a charm , There's Qik which works to broadcast live videos , and share on Youtube .