Frenzy for Mac is a social network inside Dropbox
With Frenzy, you can share links, files and messages as well as see real-time updates via a stream of feed items. The shared items and feeds get automatically synced by Dropbox, since they're all basically hidden files, and there's no signing up for Frenzy -- having a Dropbox account, whether free or paid, is enough.
Unlike other social networks that try to get you to be as public as possible, Frenzy is all about sharing with your closest friends -- provided that those friends also have Macs and Dropbox accounts. You own everything you share because the content never leaves your Dropbox folder, and, as such, you always have the option of simply deleting everything and starting from scratch (or not). That's in stark contrast to the open Internet, where once you've uploaded something, it's impossible to erase all tracks of it.
When you first run Frenzy, you pick your default sharing locations. Then you can use a customizable keyboard shortcut to share files on your computer or pages from your browser. A neat touch is that once you've shared your link or file and added your personal message to it, Frenzy immediately returns focus to the app you were using. Frenzy also lets you post status updates and comment on other people's items.
Frenzy is in public beta right now and it works on Mac OS X 10.5 or newer with Intel processors. The beta is free and will not expire, but the final version will not be free. Whether or not Frenzy ends up on the Mac App Store depends on how Apple will feel about it requiring Dropbox to function.
Download Frenzy 0.5 Beta