I don't know the situation on FreeBSD for webcams, but OpenBSD supports UVC devices through
uvideo(4).
OpenBSD also includes a V4L2 compatibility library, this allows applications written for Linux to be natively compiled on OpenBSD.. which is multitudes better than using binary emulation.
On OpenBSD, I believe the only user friendly video conferencing software is Ekiga as referenced above by
shep.
Eventually in the future OpenBSD's Pidgin port will support audio/video, but there is some framework issues at the moment that need to be worked on.