So I think I've got this data thing worked out for my 2.5 months in NY. I'll bring an external 3.5" 250GB drive, an external 2.5" 40GB drive, and a bunch of blank DVD+R discs. I think that will give me enough storage to bring most of my files with me and keep things suitably backed up while out there.
I also use this cool USB 2.0 3-drive RAID box, but it sounds like a jet. I mostly use it as a backup device, and because it is running RAID 5, I can sleep well after copying something onto it. :)
My local storage right now involves a 400GB NAS box in the closet (cheap, 2x200GB, striped) and the aforementioned 3-drive USB 2.0 box. When I travel, I use my notebook's little 60GB 7200rpm drive, an external 2.5" 40GB drive, and soon, an external 250GB 3.5" drive. I think I can put together the external 250GB drive for around $189 or so, with some deals I found today on the INFORMATION SUPERHIGHWAY (har har har). It is possible to go cheaper, but I don't want to skimp too much on an enclosure. There's a quality/price/good-deal balance somewhere. :)