I saw the Free Library of Philadelphia mentioned a few days ago and decided to check out their selection. The selection is pretty decent and I was able to find a few titles I have not seen in two of the libraries with whom I have cards. The site which shows their downloadable media is
Free Library of Philadelphia. The current ebook breakdown is:
ePub - 873
PDF - 420
I will probably register for a $15 out-of-state card in the next few days as I think I will get my money's worth from their selection.