I used the search function, honest. Google too. What are people using to unpack NV BSAs?

The FOMM (Fallout Mod Manager) is capable of doing it. I believe there's an option to associate it with .bsa file during the install process.

I use FO3Archive as my first choice (its downloaded off of Nexus), and if that can't open a bsa for some reason, I use FOMM's unpacker.

I use FOMM, it's hard to find it if you don't know it's there, it's under the "tools" menu.

Another vote for FOMM.