Now that disk space is excessively cheap doing disk based backups is much more reasonable and allows for real-time access. This doesn't solve the problem of offsite backups (unless you take an entire drive and move it offsite) but it's definately cheaper than buying a tape drive (given 250GB drives can now be had for $149).

• Arkeia Light is available free for 1 server + 2 client machines (Linux or Windows) and looks like a solution for the small time home user.

• NovaStor also offers cross platform NovaNET backup software but is definately more Windows focused. I never was super impressed with the usability of NovaStor's software when I've had tape drives previously.