I haven't been playing Starcraft for very long and I'm already looking around for strategy guides.  Right now I'm mainly playing as the Terrans and have been looking for a good guide to use for both money maps and normal maps.  This hasn't exactly been easy, but I found a couple of sites that have been a little bit helpful:

Starcraft.org has a bunch of information.  There are a few good strategies here and I learned a bunch about micromanaging flight and ground units here.  The site has strategies split up by a few different options, such as by difficulty and by whether or not it's a strategy for a money map.  There are also ratings from the users on how good of a strategy it is.

RTS Professionals is a site that I found today that has some videos showing some different strategies.  The big problem with this site is that some of the strategies have to be purchased for a couple of bucks, so I've only watched the demos videos for some of them.  They seem to have solid strategies from what I've seen, but I'm not going to start paying cash to learn them.

That's pretty well it.  I'm going to keep on tweaking the way I've been playing and hopefully I'll be able to beat my friends at the game soon enough!  I'm getting closer and closer, but during some of out larger free for all games I usually am not being able to hold out.  I'm going to try including more science vessels and air units into my strategy and see where that takes me.