How to create shaded boxes for quote?

A simple solution is provided in Blogging Basics 101 (Thanks to Jessica Knapp)

Past following code in your HTML box in wordpress.

<blockquote style="border: 2px solid #666; padding: 10px; background-color: #ccc;"> This is the text inside the box.</blockquote>

For other details see the Blogging Basics 101 page.