First there is this site, THE site to go for trophy info and help:

ps3trophies.org

This site has a trophy guide for every game released in stores on on PSN that has trophies. The guides tell you the easiest way to earn a particular trophy and sometimes provide youtube videos for finding collectibles and to show how to obtain difficult trophies. They also have what they call Road Maps. Road Maps are a straightforward guide as to how you should approach a game and what to look out for when playing to maximize your trophy hunting in as short of time as possible. You can find this information stickied in the forum for each game.

Another helpful site is

nextgenwalkthroughs.com

This site has video walkthroughs for most all major game releases. Their walktroughs are all played on the hardest setting of the game. This can be helpful for trying to pass a difficult section as they show you what to do and/or an easier way of approaching a situation. For instance for you Modern Warfare 2 players they have an entire walkthrough on Veteran up, the locations of all intel, and they are starting to put up videos for passing Spec Ops with all stars.

With these two sites alone that should help you all earn more trophies. Of course there are other sites for game help like guides.ign.com or gamefaqs.com which are popular sites.

If you have a useful site please post it.