Oprah's may be the biggest and most famous, but she doesn't own the market on Book Clubs.
One great place to find book clubs is on Goodreads. They are often organized by genre preference and have open membership to include anyone who loves a good book. I would also suggest talking to your local librarian to see if she knows of any local book clubs. You can also find them on sites like Meetup.com. And never underestimate the power of Google. A quick search of book club with your town name can pull up more results than you ever wanted.
But don't limit yourself to only local groups. Book clubs are everywhere and they all have one thing in common, a desire to read a good book. It could be yours.
Once you've found an appropriate book club (reads in your genre and is attended by your ideal reader), it's time to reach out. I suggest starting out with a brief email introducing you and your book, suggesting it may be something the group is interested in. If you want to step up your game, you can offer an web video chat with the group if they decide to read your book.
Another nice step is to let the group know that you are able to send them a discussion guide. A good guide will provide a brief Q&A that focuses on the more complicated aspects of the book in addition to a series of questions designed to provoke conversation around the books theme. So, "Who was your favorite character?" is a bad discussion question. However, "How does what MC did in X scene relate to the current debate surrounding topic Z?"
If you can swing it, sending a free copy to the group's leader is one way to get attention. Even if the group decides not to read the book for discussion, the leader may still recommend it to other members. If your publisher is open to the idea, you might also fair well offering a group order discount if the book club orders 10 or more books for their members.
For today's task, do a little research and identify at least 5 book clubs that might be interested in reading your book. Then reach out to them with your A-game.