Who controls the Bitcoin software? Is there anything comparable to a "board of directors" for Bitcoin or is the software on complete cruise-control?
There are a number of "core" developers. And the ones who have access to commit directly to the Github project obviously have more "power" than other people. Since the software is open source you can of course make your own copy of it and modify it to your likings but you won't be able to change any of the "rules" of the network unless you get the rest of the Bitcoin world to follow you and use your client.

According to bitcoin.org the core developers are Satoshi Nakamoto, Gavin Andresen, Pieter Wuille, Nils Schneider and Jeff Garzik. According to a recent message on the Bitcoin Development mailing list Wladimir (J. van der Laan?) is now also part of the core development team. Obviously Satoshi is not anymore, so I don't know how accurate the list on bitcoin.org actually is.

The ones who have push access to the Github project are according to this message:


Gavin Andresen
Nils Schneider (a.k.a. tcatm)
Pieter Wuille (a.k.a. sipa)
Jeff Garzik
Alex Waters


Gavin, who is the lead developer is active here so I'm sure he can give us a clearer answer himself. Also see Is there a list of core Bitcoin committers?