Home network backup solutions?

[Reid Rivenburgh]

Hi.  I have a small network at home consisting of one wired, always-on
F8 desktop (mine), a roving Mac laptop running OS X, and a rarely-on
Windows XP laptop.  The laptops are wireless.  I also have a new 500
GB external hard drive that some of you may remember.  The Mac user
was thinking about getting a drive for herself to do backups using
Time Machine or whatever Apple's backup app is.  But we figured there
ought to be a way to backup to my desktop/hard drive.  I looked around
and found BackupPC.  It sounds like it'd do the job, if I could figure
it out.  (I'm having trouble discovering the Mac on the network
[doesn't respond to nmblookup], and I have a feeling if I can get past
that, I will have additional trouble getting rsync or tar to work
there....)  I thought I'd check here to see if there's anything else
out there that would work.  Ideally, it would be transparent to the
clients, automatic when they're on the network, incremental....  You
know, um, everything BackupPC does!  Free and open source would be
best....

Thanks,
Reid