Here's a realtively simple way to implement data versioning in a database, in a way that should be scalable as well. It only needs a couple of support tables and a single function and can apply versioning across multiple data sets concurrently.
With the new version of OS X (Leopard) Apple has included some great functionality in Time Machine. Your Mac will automatically backup to an external drive every hour. It includes the ability to recover deleted files in a timeline.
Amazon's S3 is an online storage solution; you pay for only what you use ($0.15/GB/month, plus some transfer costs). I wrote a simple step-by-step guide to setting you a Mac to sync with Amazon S3; here's the executive summary version:
Welcome to the Git version control system! Here we will briefly introduce you to Git usage based on your current Subversion knowledge. You will need the latest Git installed; There is also a potentially useful tutorial in the Git documentation.
NOTE: This is not an official form of support. This is not an official service of Red Hat. These things may solve your worst nightmare, or they may eat all of the cheese in your house. I make no guarantees. YMMV.