If you are looking for a repository of open access fonts then Google Fonts is the best option. The Font Library, The League of Movable Type and Font Squirrel are other useful repositories. Below is a selection of fonts that I prefer:
It is possible to Sideload fonts with Kobo and Android e-readers. With the Kindle, however, it is more difficult and requires the use of Calibre (an e-book management software).