Deploy Software On Macs Connected to Active Directory?
Munki is great, I use it as well as Puppet. But for only 50 Macs? I can't see setting up that for a smaller setup unless you are really planning for scale.

Apple Remote Desktop might be a little more adhoc. It's only about $80 on the AppStore. Once your Macs are setup to allow ARD to administrate them, installing software across 50 Macs is as simple as selecting them all, clicking "Install Package", and dragging in a .pkg or .mpkg file.

It also does remote control, send UNIX script, copy files, etc. A useful tool (albeit somewhat buggy at times) for small Mac shops.

If you want a free alternative to JAMF's Composer (which used to be free), you can try Absolute's InstallEase: http://www.absolute.com/products/InstallEase