The US Patent and Trademark Office is required by law to let the public submit "prior art" for pending patents -- essentially, evidence that the thing the patent-filer is claiming to have invented already exists. People who spot patents in need of killing post them to a Stack Exchange forum called Ask Patents, in the hopes that other forum members will come up with invalidating art.
Joel Spolsky writes about how he found -- in 15 minutes, mind you -- the prior art necessary to invalidate a dumb-ass Microsoft patent on scaling images. He documents the process by which he did it, and shows how easily you could do it, too. As Spolsky points out, software patents are all basically shit, and trivial to prove as such. It just takes a dedicated army of freedom fighters to find and submit the prior art that helps the overworked patent examiners at the USPTO to reject the garbage they get by the truckload.
Software patent applications are of uniformly poor quality. They are remarkably easy to find prior art for. Ask Patents can be used to block them with very little work. And this kind of individual destruction of one software patent application at a time might start to make a dent in the mountain of bad patents getting granted.
My dream is that when big companies hear about how friggin’ easy it is to block a patent application, they’ll use Ask Patents to start messing with their competitors. How cool would it be if Apple, Samsung, Oracle and Google got into a Mexican Standoff on Ask Patents? If each of those companies had three or four engineers dedicating a few hours every day to picking off their competitors’ applications, the number of granted patents to those companies would grind to a halt. Wouldn’t that be something!