Previous Photoshop Experience...

I've had some experience with Photoshop, but very little, and none of it was taught to me. I feel like a lot of people in the PW department already know how to use Photoshop, so often how to properly use it is passed by. In 360 (I think) we did some work applying filters to different pictures, but that was my first foray into things. Since then, I've done the most work with applying filters and deleting selected colors from pictures while playing with my Module 4 banner. I would like to know how to do more in Photoshop, but I honestly haven't had a chance! And I certainly don't want to spend the 4 hours it takes to download the trial! Maybe I should just buy CS4....