We'd snag the RAM, destroy the hard drive, remove any peripheral cards that might be useful (like decent video cards or NICs), perhaps save the power supply if it was a decent one, and then after we built up a pile of them that got too big....one of us would fill the back of our truck and haul them to the metal scrap yard (just 1x exit up the highway...so a 10 minute drive). Which would give us about 100 bucks for about 20 of them.
Last week I got about a dozen newer ones together including a couple of old servers, wiped the drives with RoadKill, and gave them to a buddy that teaches shop at a tech school. They have a computer class there that he also helps teach, and he likes having lots of different computers 'n old servers for the students to learn on.