not many of em do webcams.... but who wants them really? we use video at Fermilab, but we have a posh expensive (useless) professional system.
i use kopete now but used to use gaim for multi - IM... these are the kde and gnome desktop linux applications, they have BSD/MacOS builds but i think adium is more integrated with mac.
kopete just started working with some video though. so might be worth a look.