There are dozens of free books from MG Press in the B&N bookstore today, but they can be tricky to find. Most appear to be history, legal or political subjects from a British or Canadian point of view, but I also found one about women pilots in England between WWI and WWII.
Click HERE to get a sorted list, just be careful to check the prices before buying (many are quite expensive, as you get near the end of the list). I found free titles on at least the first seven pages of results. Most (if not all) appear to only be in eReader format, so nook and PC compatible.
Update: I bought several of these and despite being marked as free, B&N apparently ran one-penny charges for each of those. No big deal to me (it's only 60 cents if you buy every one of them), but it triggered the fraud protection on my credit card (which declined the charges, but B&N put the books in my library, anyway), so it was a bit of a hassle to have to call the credit card company and get it unblocked.