Kaytlin, you are already ahead of the curve of a lot of even the "pros" here. It's great that you're willing to take the intiative and learn things on your own. Keep that up and you will do fine. Here's an exercise I used to do when I was learning. Go somewhere (Park, backyard, town square, whatever, doesn't matter, just make sure it's a relatively smallish area, so you're not too overwhelmed) and start shooting. Find subjects to shoot, and shoot them. Shoot different things in different ways. Try different compositions. Follows rules of compositions on one shot, then break them on the next, and compare and see what happened, and try to ask yourself why one looks better than the other. Set a time limit (20 minutes, half hour, hour, whatever) and as soon as it's over, go load your photos in your computer and try to critique them yourself. Don't expect to have anything great. Remember, this is about learning. Figure out where you made mistakes, so you won't make them again. Find out what worked, so you can keep doing it. I always had a fun time when I did this and I think you might enjoy it also.
I have a Panasonic Lumix P&S (TZ15) and sadly it takes better photos than my D90. It reproduces colours effortlessly and almost perfectly. The D90 is always a little washed out (colours), but that's because I've only had it a few weeks and I'm still practicing with it. I'm not bombing the thread, just trying to say that a P&S is always a great place to start and practice with.
Then again, I am a beginner myself in regards to photography. So feel free to correct me.
I have a very hard time believing this. Actually, I don't. I can guarantee your D90 will take better photos. In this case, it's likely all about presets. P&S cameras are usually preset to give most images high contrast and high saturation right off the camera. I don't know what a d90 does to jpegs by default, but with a little processing on your part, your D90 will make better photos. The key is in the processing. If you're letting the camera do your processing, you're cheating yourself.