“Flock is an amazing new web browser that makes it easier to share media and connect to other people online. Share photos, automatically stay up-to-date with new content from your favorite sites, and search the Web with the most advanced Search Toolbar available today.”
Installing it is very easy in Gutsy Gibbon: If you have a Java and flash installed in Firefox its very much a no brainer.
Simply get the package from Getdeb.net and let gdebi install it or download it and install it with sudo dpkg -i <package>
After install, Java, Flash, and al the other plugins of Firefox need to be set up in Flock with symlinking the plugin folder of Firefox (Mozilla) to the pluginfolder of Flock:
sudo ln -s /usr/lib/mozilla/plugins/* /usr/share/flock/plugins/
Thats it, should work about the same in other versions of Ubuntu, just make sure to use a .deb matching your release.