I don't know what "not a lot of money" means to you, but if you want a very sturdy, durable light with a LOT of power and a well focused spot (useful for signalling), the Salvo Rat Jr. is an amazing little light. Our LDS sells it for about $85.
Ikelite also makes a nice LED light for about $39.95, but the switch on the one we bought went bad after only a few dives, so I hesitate to recommend it.
I have a Dive Rite LED backup light which isn't very powerful, but has a nicely focused spot and a reported burn time of 50 hours, but it was a little more expensive, as is the Photon Torpedo, which, with the LED module, is a VERY bright and well-made light.