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Octopress framework

A blogging framework for hackers.

Orchard CMS

osCommerce

Open Source Online Shop E-Commerce Solutions

OpenLayers Map

OpenLayers: Free Maps for the Web

OpenCart Shopping Cart Solution

A powerful open source shopping cart system that is designed feature rich and user friendly

Optimizely: A/B testing software

Optimizely: A/B testing software you'll actually use

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Opentracker.net

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OpinionLab

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