If the size of your data is less than 4GB, a box of DVD+R's is also a cheap, secure and convenient way to make read-only backups. Just burn a new disc at the end of each workday, or whatever other interval your schedule and budget allows.

Of course this isn't really automated, but if you have one of those disc changers that people often use with audio CDs, you might be able to turn that into an automated system with a bit of scripting and hardware hacking.