David,
what subject is your ebook about and is it viral?
If it's internet maketing related, you can sign up for one of the many "Giveaway Sites" that offer free ebooks, software, ect in exchange for email addresses for their list.
The original one is Mark Henderick's, 12 Days of Xmas. Here's his email:
mark@hunteridge.com and the link to the site is:
http://www.hunteridge.com/12days/
Also, I have a "freebie Blog" where I let others know about "freebies" and discounted "goodies" available over the 'net.
Go here to check it out:
http://www.goodiesndeals.blogspot.com and if you're interested, send me a copy of your ebook for review and I'll include it in my blog
Eric