theres a website called 'adobe tv' look it up on google, it contains video tutorials on all things adobe including phothsop, dreamweaver, illustrator etc. it's very handy if you're just starting out ^_^
If you have the genuine Photoshop, the web graphic guide is Disc Two, Episode 22. In this episode, he also explains transparency wonderfully. You really should've watched all the tutorials first.
lynda.com pick up a book called "Photoshop CS4 for the Web"
Courses include the same project files that the instructors use, so you can follow along at your own pace. lynda.com tutorials are great for visual learners and people who like to learn by doing.
Is definitely worth a look for inspiration as well as tutorials and some useful tools.
Though perhaps of more interest to yourself are the 'corperate' competitions, normally logo design requests from real busuness that are free to enter and have a cash payout. It is a good way of seeing how your work compares with that of others in the same field as members will critique your work.