I recently had a number of people ask me which Blender theme I use. The Amaranth theme was originally created by Pablo Vazquez and is usually packaged with testbuilds.
I've been using it for a while because it's a nice dark gray theme that's easy on the eyes, even during late night Blender sessions. ;)
Recently though, it seems like the link to the original theme no longer works, so I decided to take the one I use and create a few different colored spins. There are 7 different flavors in this package: Lime, Mint, Navy, Orange, Purple, Red (Original) and Turquoise.
They're all hosted on my github page.