Hi Diver,
Welcome to Kindle Boards!
Due to the format that the Kindle uses, I don't believe there are any libraries that offer e-books in a compatible format. It's always possible that Amazon could update the firmware to allow other formats, but I don't see that as likely, since that would also allow Kindle users to buy books from other retailers.
Sorry to be the bearer of bad news, but look on the bright side, there are thousands of free books available through Amazon and from various other sites. I'd suggest you check out
www.feedbooks.com where you can download books to your computer and transfer to your Kindle with the USB cable, or you can visit that address directly on your Kindle and download books directly as well, no computer required.