First linux experience somewhere around age 13-16, using linux full-time as main o.s. since around 2003.
2009 - onwards SC http://sclang.sf.net
A (meta)programming environment/language. To me it is the first truly different programming language since forever, as unlike most modern languages it doesn't aim for higher abstraction and more features, but working at different abstraction levels and diminishing the barrier between the programmer and the system.
My BS thesis covered the initial year of development (avaible on project site). My currently "work in progress" MS thesis covers the meta-programming aspect of SC.
2005-10 - 2008-12 S.O.S. http://sinix.sf.net
A fairly modern graphical o.s. though very much unfinished. Most work went into the kernel, and graphics drivers (a whole lotta fun).
2011-07 - onwards Gazetracking
A gazetracking device/software strictly aimed at substituting a mouse, with the goal of vastly improved working efficiency. It's not developed in the open unfortunately, but here are some demos:
2010-05 - onwards Almost-a-DataHand
(click on geekhack.org at the bottom for the project page)
A combo keyboard, pointer (as in mouse replacement) device, optimized for mixed usage (fast switching between pointing/clicking and typing).