We keep all our code under Subversion on a server that is backedup daily. However, from the book of "you can't be too careful", I like to back my code up to an off-site area too. The off-site area happends to be my memory stick that I take home at night.
I have a Python script that iterates over my dev tree and adds all the files to a Zip file then moves the Zip file to my memory stick. A point to note regarding the script is that there's no recursion, I simply use the Python "walk" function. Very nice! You can download the script
here.