A lof of book bloggers just started receiving emails from Bostick automatically with offers of books for review. However you can get on their list yourself by going to their website: http://www.bostickcommunications.com/
and contacting them. Just explain that you are a book blogger and provide your url and mention that you'd like to be included in their mailing list.
You may or may not receive a message back saying you're on the list. You probably won't know until you start receiving emails. All you have to do to ask for a review copy of a book is reply to the email with your mailing address (and I always include my blog url). I usually add a short sentence like: "I would love to review this book." I don't know if this is necessary. You will NOT get a reply. You may or may not receive the book.
Please note that although it looks like the offers are from the book authors, they are all from the same email address as Bostick.. So save any papers that come with your book if they have the author's email so you can alert them when their review is up or ask any questions. If you want to inquire about an interview or giveaway or anything else, use the contact info that came with the book first. If nothing came, then reply to the original offer message and ask that they forward the email on.NOTE ADDED JUNE 2010:
I've reviewed for Bostick for a few years now and here are some things I've realized/learned:
1. Almost all of the books are self-published.
2. Quite a few of the books aren't good.
3. They NEVER check with you to see if you received or read the book.
4. If you don't review a book they sent you, it doesn't count against you in anyway as they don't seem to keep track.
5. If you don't like a book or don't finish it, you don't have to review it. Do whatever you prefer.
6. If you want to contact the author of the book, just send a message to Bostick asking for your message to go to the author. I've connected with a few authors this way and even asked them if they could secure giveaway copies.