photo, music, and video libraries can get very big (in my personal scenario, photos alone push 1TB). they're also the kinds of libraries of content you never want to lose. they tend to contain content that took a long time to produce, was expensive to obtain (music), or that is sentimental (family photos).
my backup situation has always been varied and unstable and tenable. however, over the past year, I found a couple of solutions that make me feel really really safe with my backups. of course, backups are only as good as your backup-restore-test-loop/workflow in order to validate that they're actually working, so "test" your backups with some regularity.
there are two types of personal backup scenarios that work for "big" backups. I employ both to ensure I'm protected in the "house burns down and destroys the disks" scenario. redundancy is a good thing when it comes to protecting your content.
The maturation of IEEE 1394 ("firewire") implementations by external disk providers and Apple allows for consistent, high throughput enough transfer rates, that you can now do backups in the background that don't swamp your computer (assuming you have a "fast" processor and I/O bus).
I just use Apple's built-in Time Machine software. For years it didn't really work, but it does now (as of a couple of years ago). If you want a heavy duty, true bootable copy, solution, I used to use Carbon Copy Cloner, and it is the best; period. I just got lazy and found Time Machine served my needs as a random end user. If I had more time, I'd probably go back to CCC.
I use a LaCie external drive connected via firewire for my local backups. Doing "big" backups over wifi doesn't work; don't waste your time.
A friend of mine pointed me to the remote backup solution I'd been dreaming about for ages; Arq. Super simple and smart local diff'ing of files that need to be backed up to the cloud somewhere. You pay a one-time local software license fee, and then you just pay the regular subscription fees associated with your cloud storage provider. I use Amazon Glacier for offsite backup, and don't have to even think about the cost of big storage as a result. Arq handles all the cloud service interaction stuff auto-magically (just give them some keys for use). Beautiful.
Arq for folks that don't know how to setup cloud storage might be a bit difficult though
With the above Local and Offsite solutions, I have a) redundancy across multiple solutions b) something fast and local should an issue arise c) something offsite (albeit relatively slow (Glacier is aptly named when it comes to data retrieval (data writing is fast))) in case the house goes up in flames.