The most practical thing to go open source according to me has been education.It started through the MIT's OpenCourseWare initiative , which plans to put all of its educational materials for its under-graduate and graduate level courses freely available on the net for anyone.
I think this provides an advantage to interested students/professionals to make most of the missed out opportunity of getting into a course at MIT.Many top universities seem to be following the MIT way and are providing their courses online.The world won't be divided now based on the quality of education with these initiatives.
Top 10 universities providing online courses
MIT Open CourseWare
Stanford Open CourseWare
CMU Open Learning Initiative
Also,to make it more convinient to search and find courses,this site would be handy :
Other helpful sites