Windows and Microsoft.
Unfortunately I started out with the limitation of Windows. I explored Win32 api's with C, toyed with MFC.
Web Development with C#, ASP.NET-MVC, ExtJS
The bulk of my work at my current job has been planning, developing and maintaing a rewrite of a massive healthcare application with several teams.
The Weird World of Perl
My tryst with the Linux Kernel:
While soul seraching on wiki.osdev.org .I started lurking at the linux mailing lists and managed to scrounge up some work. I managed to submit a few patches to the kernel. I stopped for a bit but plan to get back and try to get to more "serious" work.