Welcome to the Dark Side!!
We switched over a while ago, and now have EVERYTHING Mac, and I mean everything, except for my Mouse - I just need more buttons!
One or two books that I would recommend for you, and I have the first one on hand in standby mode for when I have that random question. It's a very intuitive and easy to find/figure out operating system, once you figure out the basics. But check out these books, they should be in your local bookstore. And in case you are using a previous version and not Snow Leopard, the books are available in earlier OS versions, you'll just have to do a search. Links below are to Amazon - just so you know what the book looks like and a brief overview.
Mac OS X Snow Leopard: The Missing Manual
Switching to the Mac: The Missing Manual, the Snow Leopard Edition
The Missing Manual books are great and they have a ton of topics, even Photoshop CS5