He uses Mozy for backing up a whole heap of his pictures from his home computer.
The basic account is free (as in, it costs absolutely nothing) and gives you 2Gb of backup from up to 2 computers. If you want more than that you get the unlimited account for $US4.95 a month for unlimited storage space and unlimited computers.
The way it works is that you download the program from their site and install it on your computer, then you tell the program what files you want backed up. From that point on, whenever your computer is not being used it will upload copies of those files to their servers. Once everything is uploaded (may take a while initially) it keeps an eye on those files and uploads the changes whenever files change.
These subsequent uploads are differential backups, so as a result only the bits that have changed get uploaded, which means a lot less bandwidth used.
Your current backup is permanent, and old backups are kept for a month, so old versions of files (and deleted files) can be retrieved for up to a month afterwards.
If you click on that link and sign up, the system will know that I have referred you (which is the extra bit after the base url) and as a result I will get an extra 256Mb of backup storage, and so will you. Yes, that's right, if you join from a referrer, you also get the referring bonus. Neat! If you don't sign up straight away and come back to just the normal page, you can put in the referral code of "FA8PMI" in as part of the signup process and we both get it again.
This looks like a really useful thing, and I'm intending to use it for a little while and if it works out probably sign up for the unlimited account later.