Couple of days ago Adobe published Source Sans Pro a nice open sourced monospaced font. You can download it from Sourceforge.
Read some more detailed information here:
Personally I have tried it in a terminal and in IntelliJ and on TextMate. It really didn’t convince me and I removed it after 10 minutes of using it. I got an headache and my eyes were hurting. But it looks nice somehow, but for heavy usage I won’t recommend it.