Two best sites are:
Flashlight Reviews

Candlepower Forums
Candle Power Forums has been going down from time to time this week - server problems.

The cheapest and quickest way to turn a Minimag into an LED flashlight is to pop in the 3-Led head which is sold by Nite-ize. It runs between 6 to 10 dollars, depending on where you buy. It is not the most powerful mod, but it will give you a nice beam, LOOOOOONG battery life, and durability. I rate the beam quality as a little bit better than a stock Minimag. The more powerful modifications come at the expense of cost and battery life.