There are also quite a few good 1/350 kits of ships from the "pre-dreadnought" era, all usually under £20/$30:
Revell SMS Emden/Dresden (German light cruiser)
Zvezda/Eastern Express Varyag (Russian cruiser)
Zvezda/Eastern Express Borodino, Orel, Suvorov (Russian battleships - all 3 are basically the same kit with minor changes)
These might not appeal to everyone as much as WW2 or modern ships, but they're great kits for the price, and the cruisers are about the same level as a WW2 destroyer in terms of complexity and size (even the battleship isn't too large, though it has a lot of secondary guns which could be tricky to assemble and paint)
I built the Emden recently, photos of my build are on the forum at http://www.modelwarships.com
EDIT: If post-war/modern ships are more your area of interest, Dragon produce a number of USN destroyers and cruisers in 1/350 which are good kits, reasonably cheap and not as complex as a battleship or carrier.