Just this morning the Gallium3D pipe-format-simplify branch was opened up by VMware, which cleans up the pipe format header file. The discussion surrounding pipe-format-simplify can be found on the Mesa3D development list.
Meanwhile, Roland Scheidegger is preparing to merge gallium-strict-aliasing to Mesa's master code-base. The gallium-strict-aliasing changes the Gallium3D API, but actually allows for Gallium3D to be built with strict-aliasing C99 compliance, which can lead to performance improvements assuming no incorrect code assuming all goes well. The gallium-strict-aliasing is discussed here.
Prior to gallium-strict-aliasing, Roland was working on gallium-noblocks. This is another API breaker to Gallium3D, but all of the state trackers and drivers should be already fixed. The gallium-noblocks branch is discussed here.
There is also various other improvements and changes going both into Mesa and Gallium3D. All of this work will likely end up in Mesa 7.8 to be released in H1'2010. Mesa 7.7 meanwhile will be released later this month.