I use Crashplan too. It is free, easy, and here is the key ... easily implements redundancy. The whole point is you can backup to multiple "destinations". It has Mac, Windows, Linux, and Solaris clients. One of the cool things I do is run it headless on my Linux server. I can log into the GUI remotely using port forwarding from my Mac. Here is my backup scheme:
a) Directly connected USB drive (which has 2 partitions ... I use one partition for Time Machine and one for Crashplan. This is my main/most important machine w/ pics, music, movies, documents, etc.).
b) To my Linux file server. The file server is ClarkConnect (a Redhat/CentOS based Linux distro that does a bunch of cool things by the way).
c) To my work laptop. Runs XP.
Work laptop (WinXP):
a) To my Mac.
b) To my Linux file server.
Netbook (running Win7):
a) To my Linux file server (I hardly keep anything unique/important on it).
Linux file server (ClarkConnect):
a) To my friends file server. I let him use my Linux file server in return.
b) My parents computer. They don't even know it. They use their ridiculously overpowered Dell with Vista as a "super magic email device" and Solitaire machine. I put in an extra big honking HD when they got ...and installed free Crashplan. It hums along quietly without them even noticing.