IP backup solutions?

[Brian]

I need to backup some Winders machines in a remote location (California)
to a server in Massachusetts.  I could do this by paying Veritas a bunch
of money and running the backup on a Win2K box, but I'd rather not.

However, I haven't (in my admittedly narrow search) found a linux-based
IP backup solution that is optimized for sending lots of data (many
gigs) over a slow pipe (T1 in this case) (ie: compression, good
differential backup handling, etc).

Any suggestions / input / comments / funny looks?

Thanks.