This is a re-post... but I was asked to share it again. Here's a free (and really good) way to learn all about the Adobe Camera Raw plug-in. This is a bonus eBook I wrote to go along with the book Understanding Adobe Photoshop CS5. Its yours for free... I hope it helps.
Be sure to also check out the new book – Understanding Adobe Photoshop CS5
Here's a nice review of the book too – http://www.mymac.com/2011/02/book-review-understanding-adobe-photoshop-cs5/