Canon S series - Raynox 730 Debarrelized

Though the Raynox 730 shows the most barrel distortion...

Imaging Factorys Debarrelizer

...it can easily be corrected by software.

Place your cursor over the image to see what it looks like when Factorys' Debarrelizer imaging software is used, a one slider adjustment that took only a few seconds.

Or try Panorama Tools - freeware for Photoshop 5.0 or higher, and Photoshop Elements 1.0 or higher with a tutorial courtesy of dpreview.