In my opinion, hard drive backup solutions are the most cost effective currently for single user systems. Its much cheaper in terms of effort and overall data continuity. They are also dynamic. For example, I have a 500GB system drive, 1TB backup internal, and a 1TB backup external. The system drive is used for normal day to day use. The 1TB internal contains system images as well as mass storage for all of the files I consider important or critical to me. The 1TB external is maintained as a duplicate to the internal 1TB, and thus provides redundancy to the backup. With this setup, I can lose either internal drive and still be fully protected, and since the external is used sparingly just to update the backup, wear and tear is kept to a minimum.
Some would consider this overkill, but given how cheap hard drives have gotten lately, it really is worth investing a couple hundred dollars in a virtually bulletproof backup solution that doesn't rely on raid support in any way. True, its a bit more hands on than some would like, but isn't data integrity the number one goal?
As for dvds and blu-ray. I think these are viable backups, but considering the cost of media and the tendency for bad burns (which sometimes aren't caught unless you do a full read test at write), i wouldn't trust anything important on them. Plus over time you have to destroy them as you make new ones, which is throwing money away. I have never felt that re-write discs were reliable enough.