Flock is a social browser based on Mozilla Firefox engine. Flock 2 beta two released now, this version is based on Firefox 3 and Flock 1 beta 1 is based on Firefox 3 beta.
The new version has all the great features of Firefox 3 and the Flocks social features. If you are already using Flock beta 1 then you can upgrade to this version. Remember this is a beta version so backup your profile, bookmarks etc. via Mozilla Links