[Lilux-help] voip, im, video conferencing etc.

Hi, possibly for a future conference, but also to simply play around, I'd like to study the quite large field of VoIP (voice over IP), IM (instant messaging), video conferencing, if possibly everything out of the same box (which might be interesting for, say, internal use in an organisation). My experience so far is limited to plain IRC and once-upon-a-time a bit of ICQ, Google provides rather too much information at once. Starting with hardware: can anyone recommend specific stuff like headset, webcam etc. that will work under GNU/Linux, preferrably with free (as in liberty) drivers? VideoConf / a/v IM: is there specific software to recommend for this task? At first sight, there's rather few IM clients that implement audio/video stuff for instance, even if there's special clients for 1-on-1 "video phone". Preferrably, clients should support multiple protocols / providers, and be multi-platform - at least interact with other, proprietary clients. I've started looking at clients like kopete, gaim, kphone. What about the server end? For VoIP the usual suspect would be asterisk plus a few others, for IM there's always IRC, jabber, ...? For the tests, I guess I won't need VoIP access to the normal phone system, but it might be interesting if it can be implemented via a simple ISDN line [possibly using a few MSNs], or via a (cheap) external provider to which one could connect the local VoIP server. I'll certainly check out VoIP articles in one of the past german LinuxMagazin, which had a special not too long ago. The interesting thing here would be some sort of integration of VoIP and IM (address books etc.). I do want to use open standards, so Skype is out (but still might be fun to test). I guess I needn't mention that all should be FOSS, and shouldn't lead to hefty expenses for telephony providers etc. Bandwidth use is less critical, but will be interesting to test for (i.e. use as little as possible for decent quality). Thanks for any interesting input! Greetings, Eric