stripboard (sometimes called Veroboard) is probably the cheapest option. Widely available and cheap.
Strangely, this isn't true in the United States. Pad-per-hold is popular, and there are the proto-board-like PCBs that are sorta nice (RadioShack.com Official Site - America's Technology Store ), but cheap stripboard never seems to have caught on. Of course there are a bunch of mail-order dealers that fill the void...