Well, this shop-script is not as well known as Magento, but it offers same functionallity (nearly) and is much more lightweitght for sure, most of features are being still developed, however team released 1RC for our developers needs today.

This release however is under TESTING ONLY tag so far, still yet its feature reach (View feature list here) free and lightweight, you can checkout demo here: http://www.prestashop.com/demo.php

Not bed for 3.0MB ha? You bet, give it a ride.