Almost every web 2.0 developer has dabbled with PHP at least once in their lives, and though some praise Ruby on Rails or other framework, some live and die with PHP programming. I’m one of those PHP die–hards that would use it over anything else, as long as it is still possible.
Now if you’re one aspiring web developer or designer, or one of those special cross–breeds that excel in both, you’d love this site that lists countless free PHP books. Yes, free! Also listed on the same site are resources for other programming/computing topics that can be very useful for everyone. This one goes into my bookmarks.