Here's the link for
NOOK for Web.
To get the six free ebooks that Phoebemy listed, you need to have a credit card on account at Barnes & Noble. At the end of the book sample, there's an icon that says "Nook Book $0.00" in the upper right corner of the screen. Just click on that. You don't need an account if you just want to read samples.
Amazon's Cloud Reader is
here.