I have found Ghost for Unix and Ghost for Linux very effective at creating images and storing them over the network. The best part is that the server side needs only be a standard FTP server, so you don't have to worry about getting some proprietary server software installed and updated.
I have used both G4U and G4L to create and restore images of Linux and Windows machines many many times without any problems. Personally I like to use G4U simply because of the controversy
around G4L. But I often find that the driver support on G4L is better, not to mention actually having a GUI (G4U is all command line), so I have to put my morals aside occasionally.
Another great program is partimage. I find this is more effective for Windows systems, since you can only make an image of one partition at a time, rather than the entire disk (which 90% of Windows installs are). Partimage has it's own server software, but you could just as easily mount a NFS share off of your main server and backup/restore to that if you would rather go that route.
If you want to stick with only one program for all OS's, then I would definitely go for G4U/G4L. Download both of them, run a test backup, and find out which one you feel more comfortable with. They both use the exact same methods (dd of the drive pushed out to FTP) so there should be no performance differences, it is just a matter of preference. In fact, I suspect the resulting images would work with either program, but I have not personally tried it.