Think of wikipedia but one with real time edits… Sharejs can help you build it.
It lets you easily do live concurrent editing in your app.
I found this awesome website unheap.com. These guys collect some really cool jQuery plugins.
You can browse plugins by type (interface, inputs, media, navigation, or other). They’ve taken the efforts to link the demo page from the listing itself. So you don’t have to run through hoops to checkout the cool demos. Awesome work!
Here are some very cool jQuery plugins I discovered via unheap.com -