So, I'm getting twitchy that my existing backup solution isn't enough - I need to do something more.
This is what I'm doing today:
iMac with 1tb onboard. This is where my 2011 Aperture library lives. That is Time Machine'd off to a 1tb Time Capsule that is almost full.
A 2tb USB2.0 drive with all my archive libraries and photos on it. They are archived to a 1tb USB2.0 drive, with monthly updates.
Also on the 2tb drive is a bunch of recent video stuff (nothing critical) that isn't backed up anywhere due to lack of space.
So, thats today.
I've got a budget of about $300 to $400, and my current thought process is to:
pickup a 4tb WD MyBook II or a Drobo with about 4tb of drive space in RAID1.0 (so, 2tb usable) and have that as my main drive, with it archived to the USB2.0 2tb drive. Use the 1tb USB drive as a time capsule for my local, onboard disk.
Thoughts? I like the historical archives of Time Machine, which is different to RAID1.0, but I don't know how important that would be ...

I'm running out of local backups space too - hence the need to upgrade. I'd likely recycle some of these now redundant (hopefully) drives once I have something extra locally. 
