One of the niftier features of the Kindle Store is the way that it lets you embed a sample of an ebook in a webpage. Now there's an option for indie authors to do the same with just about any Epub file, albeit in a slightly more complicated and less convenient way.
A Japanese developer by the name of Satoru Matsushima has released a self-contained Epub viewer which can be installed on most websites. It's called BiB/i, and all that is required is for you to upload the code for the viewer as well as the ebook you want to embed, and them post the embed code.
The embed code looks like what you would see with the manual (non-automatic) Youtube embedded videos, so some technical skill is required.
I haven't installed it myself on this blog, but as you can see below it does work:
You can find other demos here.
The code works well, and you can even use BiB/i to open an ebook sitting on your computer. Simply open the ebook embedded above, switch to full screen, and then drag another EPub file into your web browser.
This won't work so well for large ebooks (for those it is recommended that you unzip the ebook file before uploading it) but I did just test it myself. I was able to open a couple different Epub files. They were slow to load at first but I could read them.
I've just heard of BiB/i, so I can't tell you if it is in widespread use yet, but I do know of at least one alternative (besides uploading a sample to Scribd and embedding that). There's Epub2Twitter, which lets you embed ebooks in a Tweet, and ReadK.it, which enables authors and publishers to create self-contained ebooks which can open themselves in a web browser (as well as regular ebook apps).