[Hampshire] Cross platform (easy) video conferencing

Hi,

I'm looking for a good protocol/set of applications/web cams for linux
so that I can video call (not really a conference) my family/gf's
family when were in Australia later this year. I have a few
requirements:

- Webcam that works on linux (of course).
- A protocol which has free/open source applications both for linux/windows.
- A protocol that requires minimal port forwarding and stuff like that
(like IAX).
- A protocol that doesn't need a paid for service.

Best case scenario would be a way of getting a video call to work
between my linux machine and my mum on msn messenger. Ease of use is a
factor, but getting something that works is obviously more
important..although it would definitely be nice to not have to tell
all my friends/family how to use something really complicated.

Thanks everyone!
John.