What lesser known free and open source software do you use daily to improve your life?

The funny thing is that when Chrome was first released, I was pretty excited that open source web engines were becoming more widely adopted.

Whatever one thinks of the current dominance of Chrome, I vastly prefer it to the time when Internet Explorer 6 had >90% market share. Open standards and FOSS technologies really are a winning cause even if the end products aren't always FOSS.