According to Apple, AirDrop will be listed in a Finder window sidebar. Click AirDrop and you'll see a list of Mac users with AirDrop enabled who are connected to your network. To send a file, simply drag it to a user's name. That user will see an alert that you are sending a file, with the option to accept or reject the transfer. If he accepts, the file will be added to his Downloads folder.
There aren't many third-party options that mimic AirDrop, but DropCopy is a free app available for Macs running Snow Leopard, Leopard or Tiger. (It's $4.99 if you need to install it on more than three Macs.) Its goal is essentially the same as AirDrop's.
When installed on two or more Macs on a local network, an icon called the Drop Zone appears on the desktop of each. Dragging files to the Drop Zone will display a list of available Macs with DropCopy running. Drag the file(s) onto a specific Mac and it will copy to that Mac. (Users specify where they want copied files to be placed when they install DropCopy.) DropCopy also allows you to transfer contents between the clipboards of two Macs.
One major difference between AirDrop and DropCopy is that AirDrop requires user confirmation before a transfer takes place (a big plus when connected to public or office networks), whereas DropCopy does not.
Note: A version of DropCopy for iOS is also available; it lets you send files on a Mac to an iPhone or iPad (or vice versa), or share files between two iOS devices.
More multitouch gestures
Apple has been bringing multitouch features into Macs for a long time now. The original MacBook Air pioneered the use of the trackpad for multitouch gestures -- pinching, swiping and the like -- in 2008. Apple has expanded these gestures in more recent MacBook models, as well as in its Magic Mouse and Magic Trackpad peripherals.
In Lion, Apple has promised to bring even more iOS-style multitouch gestures and visual responses to Mac OS X. Among the new gestures demoed on Apple's Lion page are rubber-band-style scrolling, enhanced pinch and zoom functionality, and full-screen swiping. Whether Apple will offer even more advanced gesture support is an open question, but I wouldn't be surprised to see some more in the final release.
If you don't want to wait to get more gestures and capabilities, however, you don't have to: There are several utilities available for getting your multitouch groove on in Leopard and Snow Leopard (but not earlier Mac OS X releases).
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