We made our own, which we think is cool. Yintersync, (http://www.yintersync.net)
Its a Rsync inspired windows replication tool for countless servers, desktops, laptops etc all managed from a single interface. It has VSS support, email reporting, compression, scheduler, compression and a fast hashing algorithm strategy yet only 32kb block size.
We use it to replicate Hyper-V servers from all our customers sites back to our location for DR well as a backup product for all our own data (in combination with removable disks and shadow copies).
Its still in beta but we are using it in production on about 70 servers, ~10tb of data, millions of files over a mix of LAN, ADSL and FTTC connections without issues. The beta we released yesterday is probably the first one which might be usable in production.
If you use windows, try our tool. Originally a rsync wrapper but we ended up designing our own delta encoding method which we find works a lot better than rsync/cygwin on windows.
We use it to pull data back from customer servers on all sorts of rubbish connectivity.
We use our own tool http://www.yintersync.net to replicate our customers data to a cheap server or old desktop. It uses rsync like delta-copying to keep system and bandwidth requirements very low (we backup lots of Hyper-V systems over links as small as 1mbit).