If I can't dl a .mobi from A03, I make a .pdf (google docs will do this if you don't have any other way) and drag/drop or c&p into the documents folder of Kindle since it will read .pdfs. When I do this, I try to enlarge the text so it's more readable. I've been reading all my fic on my Kindle for the last year and a half, and it works a charm, esp. for long fics.