If you own a prestashop web store and have been wanting to connect it to Authorize.net, you've probably noticed there's a plugin on their website for nearly five hundred dollars.  I'm pretty cheep and as a developer I just built my own and am offering it here for $99 to prestashop users who would like to purchase it.
Mine does everything, integrates nicely with a drop in plugin and has a custom checkout form page for any design you like.  It also saves the log-in and keys from the back end so there's no code to change!