Yes, it is basically a movie about Al Gore giving a slideshow. Go ahead, get the jokes out of your system ("Perhaps we could put global warming... in a lock-box.") And then once you're done snickering, go see An Inconvenient Truth. It's really very good, and it's really very important.
The most frustrating thing about the movie is knowing--knowing--that if you try to talk to someone about it (and it really does give you a drive to action, makes you want to save the planet), they're probably going to bring up the same tired objections that all ignorant people use against global warming. "I'm not convinced it's us," they'll say, or "I heard that wasn't solid decided science yet." (Right: because "teach the controversy" has turned out to be such good, ethical advice.) And all those kinds of questions are actually answered by the movie. Gore explains why it is man-made, why there is no scientific controversy, and why we have to make changes now. It is a chilling demonstration, even as he delivers it with wit and good humor.
There are really very small things we can do. Change your light-bulb for one that uses less energy (it'll last longer, too). Move your thermostat up or down by only 2 degrees. There's more good advice at the movie's supporting website, ClimateCrisis.net. You're helping the planet, and you're lowering your energy bill. You'd honestly have to be malevolent to not support this fight.
I know I'm a soft touch, but I honestly walked out of the theater fired up and looking for ways that I can help. One of them, I hope, is to encourage you to go out and see the movie--but even if you don't (and I understand, money can be tight and it's not out everywhere), just take a look at ClimateCrisis.net and see how you can help yourself and the planet at the same time.