http://wpkg.org/
It's no turnkey solution, you're gonna have to configure it. It doesn't work with
every program but it works with a lot of them. I used it to help with initial software installs and keep several programs up-to-date over the course of several months (until we decided to switch to a minimal software set to overcome some compatibility issues and in light of a better handle on user requirements).
It requires an initial install of the wpkg client, usually manually or possibly by other software management. But after that everything is handled from the config files on the server. It can work with
any SMB file server - Windows, Linux, NAS, whatever.
In conjunction with
http://www.wsusoffline.net/ you can use it to handle Windows Updates. This avoids having every computer in your office download the updates individually, reducing your bandwidth usage.
Note I never got WPKG to work right with wireless networking, it seems the WPKG service starts before the network is up and so errors out. But if you're using wired it should work fine.