Akshay Gupta, a GSoC student, has posted some very interesting videos in which he shows the current progress of integrating Activity Journal (powered by Zeitgeist) into GNOME Shell:
There is still a lot of work to do, the goal being something like this (mockup):
One thing that's not very clear is how the Journal will integrate with the new GNOME Shell design (mockup posted by Jakub 'jimmac' Steiner):
But there's enough time to figure that out until GNOME 3.2 is released (sometime around September 28).
For more info on The Journal, see Akshay's post.