For new writers who are still looking for a distributor, I recommend Smashwords. It’s probably one of the biggest e-book distributors around at the moment, and is an excellent way to get your work out there that won’t cost you a cent.
Authors upload MS Word manuscripts, and Smashwords’ Meat Grinder converts it to the most popular e-book formats. Once your manuscript is approved, Smashwords sends it to various distributors, including Barnes & Noble, iBooks, Kobo and a few others.
The author sets the price of each book, payments are made via PayPal, and you get your own profile page on Smashwords.
I’ve published my books on Smashwords, and I’m reasonably happy with everything so far. There’s the odd thing or two I’m not completely charmed with, but then you’ll find that it’s the same no matter who you use to sell your books.
I’d love to hear your experience, both with Smashwords and other distributors/aggregators.