I have now reached over 6,000 pictures in my image database (managed with iMatch, of which I've categorized about 90% of it. iMatch's category system is so incredibly powerful), which I think take over 12 GB of space (which it all resides on my laptop hard drive... not the most secure solution). This doesn't include all the Photoshop work (which is a few GBs of its own!)
I've been thinking about how to deal with this. What I'd like to do is a NAS (network attached storage) RAID (redundant array of inexpensive discs) system. Tom's Networking has reviews of a bunch NAS solutions, (a few of which can go up to 1.2 TB). The one with the highest recommendation is this one (albiet fairly pricey, but comes close to reaching that $1 per GB ratio). It also supports RAID 5 (quite cool).
Ideally (if money weren't an option), I'd put together a gig-e network and attach a NAS RAID product. Oh well. I'll figure out something.