What Source Library do you use to add ebooks to your library?

I recall reading a thread somewhere in Talk discussing where folks found good Source Libraries to use (for Add Book) in order to add ebooks to their catalog, so they wouldn't have to do a manual add. Now, of course, I can't find that thread. So, I bring my question to this group. Do most of you use a library source (if so, which ones?) or a manual add for your ebooks?

I am adding using Amazon using whatever ISBN comes up then I use a tag "ebook". If I find a source that will accept the eISBN, I will post it here.