I've found ebook reader websites so useful during promotional giveaways that I've written a blog with tips I've found so far. This includes links to more than 50 sites which invite submissions for free, which ones need a month or two weeks' advance notice, which ones only want to hear on the days of a giveaway etc. Also, how to prepare in the weeks leading up to a promotion. Hope it helps you out. It made a big difference for me using these techniques. More info in the blog post on
http://www.adeleward.blogspot.com 