Airdrop Alternative for Windows/Mac/Linux?
Have a look at Transfer on Lan - it's not as full of hardware encrypted, peer to peer mesh network goodness as AirDrop, but it's the closest stand in for AirDrop that I've seen in a cross-platform client.

http://code.google.com/p/transfer-on-lan/

It uses a normal network as opposed to building up a secure temporary network, but other than needing java, it's pretty easy to implement.