All books that are not copyrighted can be accessed quickly. Many books have excerpts that are likewise easily accessed (through a direct link via Amazon).
For a list of free ebooks good for students, see this bookshelf:
The embed code is available for inserting into another website, e.g., this is the code for the book above (which unfortunately doesn't work in Google Sites -- or, rather, I haven't been able to figure out how to make it work yet).
<iframe src ="http://www.goodreads.com/reader/2317?percent=0.0&widget=1" width="100%" height="100%" id='readerFrame'>
<h1><a href="http://www.goodreads.com/book/show/46165.This_Side_of_Paradise">This Side of Paradise</a></h1>
Your Browser Does Not Support IFrames.
<a href="http://www.goodreads.com/reader/2317" only_path="false" target="_blank">Click here to read the e-book on Goodreads</a>
</iframe>
<center>
<a href="http://www.goodreads.com/"><img alt="Goodreads.com" border="0" src="https://www.goodreads.com/images/widget/widget_logo.gif" /></a>
</center>
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