www.wetcanvas.com/Articles2/2123/226/index.php
Thats an interesting beginners tutorial that teaches you about some of the basics. If you use the help bar that shows you alot too, like if you're not sure about some of the tools just look it up in the help tab.
one thing I never found out while I was messing with photoshop that is super super useful..
to ADD to a selection once youve already selected something else (i.e. you wan't to select just the eyes on a picture) you hold shift while selecting the second selection and it selects them both.
and to take away from a selection (say you want to select an eye but not include the iris) hols the alt button while selecting the area you don't want included.
hope that helps ^.^ -MontiK