Bookbub.com is a great place to advertise your ebook, if your book has a lot of reviews. Just learned that yesterday. So now the strategy is to get reviews. Anyone who purchases my book Fugue in C Minor (it is available on Kindle at Amazon.com), please post a review there and at goodreads.com. It really helps indie authors when readers post reviews.
There are lots of places to market a free ebook, but then the author doesn’t get paid.