Teens were the vanguard for instant messaging and now tend to be heavy users, keeping multiple windows open and conducting several simultaneous conversations with friends.

FORBES: Just Speechless

It's a wonderfully minimalist app, if that's your thing, and you can open multiple windows (currently through a keyboard shortcut) to get some of that TweetDeck-style power user layout.

ENGADGET: Tweetbot for Mac arrives as free alpha, we give a quick hands-on

Any number of people standing in front of it can put their hands on the screen and "paint, " or pull up satellite maps and zoom in on different locations, open and collapse multiple windows of Web video.

FORBES: Radical Ideas