Solid-state drives might have weight, speed, and physical size working in their favor for portable use, but hard-disk drives still win in capacity and price. The Western Digital Scorpio Blue HDD is proof, now going clear up to 500GB in size at an MSRP of $219.99 (and likely found for less soon).
It only spins at 5,400rpm, but uses WD's WhisperDrive algorithms to find your data with less searching, translating into less noise and better battery life.
The 500GB Scorpio Blue drive would make a nice portable external drive as well. Just pop into an enclosure and you've got a ton of storage at your fingertips. Plus, it uses WD's ShockGuard technology that keeps the recording heads parked when they're not in use.
The 500GB drive is shipping now, as is a 400GB version for $189.99.