Better than the Jetpack mobile plugin, discover how to make your website responsive!
Almost nothing to configure, absolutely brilliant!
The plugin replaces automatically your theme. At the bottom of the page, the user can still choose to go back to the classic desktop theme.
To know which other plugins I am using on CarmaBlog, you can read my previous post.
You want to know how your site looks like in different smartphone browsers (iPhone IOS, Samsung Android or BlackBerry RIM)? This website is the one I used to do the screenshots and works pretty well.