What is your spending limit? There are A LOT of great lights out there. A great light is the NiteRider MiNewt 600 Cordless, depending on where you buy it anywhere from $110 to $150 and it does a very good job of lighting the street up. My light right now is a NiteRider 1500 Race which will set you back about $350 (I got it on sale @ nashbar for $250). Thee NiteRiders are great for the trail because they throw a wide beam pattern so you can see everything around you.

I like NiteRider, but a lot of others here will suggest different brands that are just as good - Dinotte, MagicShine, etc. There is also the option of getting a high-lumen LED flashlight and lashing it to your helmet or bars. I think a great light for you would be that 600 Cordless I mentioned above, I think you can get it at Amazon fairly cheap - -

Here's a great comparison from mtbr, comparing many lights. I used this comparison to choose my current flamethrower. http://reviews.mtbr.com/2012-bike-lights-shootout