Glenn Fleishman explains a tiny tweak you can make in Lion that enables AirDrop peer-to-peer file exchange to work over local area Ethernet and wireless networks. This enables AirDrop for older Macs that lack the right Wi-Fi chips to work with AirDrop out of the box, and it also adds wired LAN access for even those Macs that do have supported Wi-Fi chips. follow link
Using Expose within Spaces
To drag a file into an application that's running in another one of your Spaces, use Expose while in Spaces overview mode. First, press F8 to go into Spaces overview mode, then press F9 to Expose all application windows. Hover over the application window you want and wait a moment or press the Space bar, and both that space and that application come to the foreground, ready for you to drop the file.
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Enable AirDrop for All Macs with Lion
Check out the Take Control ebooks that expand on the topic in this article: