Looking for recommendations for collaboration tools

I have a client in Toronto and we need a way to collaborate on projects. By
collaboration I mean view a text document and mark it up in real time and
talk to each other.

We have used Instant Messenger, but the "typing bandwidth" is too low for
discussing issues, and we cannot markup a document in real time. The phone
is too expensive for some of our marathon sessions, and his cell phone
reception is poor at best (he does not have a land line in his apartment).

Is voice over ip a possible solution for better communication? How does one
go about installing it (whatever it is - I assume there is a client that
needs to be installed?)? How much does it cost?

Any suggestions for a real time text document viewing/editing application?
The document is Java code, so we must be able to save it as a text file.

Oh, and finally, one of our computers is Linux and the other one has one of
those funny Window's icon at boot up.....;)

Any suggestions that are free (or low cost) would be greatly appreciated!!

Thanks!

Mark Phillips