I use open source every day software every day. We would be nowhere without it. Here's a short list of some of the projects I've contributed to over the years. This list is incomplete. Check my github page for more up to date list.
The missing package manager for OS X.
Ruby library for reading Bencode format (used by bittorrent among others).
Internationalization library for Merb.
A plugin for Jekyll blogging framework for specifying multiple URLs for one page.
I contributed a patch for the MerchantWarrior gateway. I created this patch for a client.