OTish: Alternative to MS Live?

[Kurt Buff]

All,

Our new CEO wants me to poke holes in the firewall and install the MS
client on a number of desktops to facilitate IM/videoconferencing for
this.

That makes me vaguely nauseous, for several security reasons (the
client is historically vulnerable, poking holes in firewalls is risky,
and internal corporate communications should stay internal - that'll
do for a start...)

I'm looking to stick an IM/Videoconference system in a DMZ instead.

Does anyone know of a good alternative - preferably with a web
interface, though that's not absolutely required?

Thanks,

Kurt