This is going to be short, because there isn't much to say: I've been using the Real Triggers for PS3 for a few weeks, and I love them! They are little plastic clips that slip over the L2 and R2 triggers to make them more like, well, triggers. They are < $5 for a set and it is easy to move them from one controller to the other.
Highly recommended.
I got mine from Amazon, but I'm sure they are available elsewhere.
http://www.amazon.com/PS3-Dual-Triggers-Playstation-3/dp/B001IAOEXU/ref=sr_1_1?ie=UTF8&s=videogames&qid=1262224081&sr=8-1