Today, DropCopy still deserves a place on your Mac, as it does a few things that AirDrop doesn't.
For one, DropCopy can auto-accept file transfers. Meaning, your recipient needn't be in front of his/her machine to initiate or accept a transfer. That's handy if you want some files to be waiting at a remote work station upon your arrival.
DropCopy also passes the contents of one machine's Clipboard to another, creating a handy -- albeit makeshift -- inter-machine link.
The way it works is similar to AirDrop. Just drag-and-drop your file onto the Dropzone and it'll show all the possible destinations. Participating machines must be running DropCopy on the same network. Simple.
If AirDrop just doesn't cut it for you because you're on a non-Lion Mac, you must send files to a non-Lion Mac, or you need to send files across a wired network, DropCopy is the answer. It's available in a free 3-machine limited version or a Pro version for US$4.99 from the Mac App Store.