The Frugal Girls posted about 'Ruby' being free. Check out the links on their page here: http://bit.ly/TNV9Qc The book is available for Nook and Kindle.
Harlequin.com is giving away books through February for their KISS collection. This week's free book: Waking Up Married. Find it here: http://www.harlequin.com/sampler.html?sampler=KISS
And of course, Amazon has a huge list of free books here.
As does Goodreads here: http://www.goodreads.com/ebooks
Then of course, the Nook selection of Free books, sorted by genre: http://www.barnesandnoble.com/u/Free-eBooks/379003078/
Happy reading!