Blender is scriptable through the Python language. I've never scripted Blender and I've never used Python, so it took me a bit... Figuring out the appropriate Blender APIs and then learning the Python syntax (it is very different from what I'm used to like AS3, C# and Java). Here's my tiny, first script:
objects = Blender.Object.GetSelected()
for curObj in objects:
curObj.rbFlags = curObj.rbFlags | Blender.Object.RBFlags.RIGIDBODY
Taking it apart, the first line imports the Blender module for the Blender APIs. The second line gets all of the selected objects in a scene using the Object module's GetSelected() method. The third and fourth lines iterate through the list of objects. Line 4 uses the bitwise OR operator to set the RIGIDBODY flag for the current object.
It took me a while to figure this little script out, longer than it took to do the operation manually. But the next time I need to set a property of a large number of objects -- any property, bitwise or otherwise -- it'll take seconds to type instead of minutes in the interface.