Anonymous Pro is an open-source monospaced font released in 2009. It was designed by Mark Simonson — the same guy behind the ever-popular Proxima Nova font. Anonymous Pro is unique for a monospaced font in that it contains normal, italic, bold and bold italic styles. I think it makes an excellent programming font.
If you are looking for an alternative to Anonymous Pro, I recommend checking out Inconsolata and Maison Mono. I think Neuzeit would make a nice font combination with Anonymous Pro.