For off-site backup, a service such as Mozy is a good choice. There are a number of different alternatives, but I recommend Mozy because it works with both PCs and Macs, and because I use it personally. I have heard good things about other services, such as Carbonite, I just have not used them myself. I have used CrashPlan in some small offices, and it worked great too.
Finally, none of this is any good unless the backups are actually performed. The backups need to be automated so they happen without any input from you. That way you can let the backups do their thing and only check from time to time that all is well. For this reason, Mozy performs your off-site backup without any input.
Give Mozy a try. You can get an account with 2 gigs of storage for free! Then, if you like it and decide to go to a full unlimited account, you can pay less that $5 per month for the service.