Mesa 7.8 Release Candidate 1 was announced by Intel's Ian Romanick in a mailing list message that just contained the MD5 check-sums for the files. Mesa 7.7.1 Release Candidate 1 was also announced in the same message, but that point release is just carrying bug-fixes atop Mesa 7.7 that was released last December.
For those that have not been following the development of the Mesa 7.8 release, it's including the new OpenGL ES 1.1/2.0 state trackers for Gallium3D, new Gallium3D documentation, much improved EGL support, and support for new OpenGL extensions. The new OpenGL extensions to be found in Mesa 7.8 include GL_NV_conditional_render, GL_EXT_draw_buffers2 extension, GL_ARB_fragment_coord_conventions, GL_EXT_texture_array, and GL_APPLE_object_purgeable. There's also support to the different DRI drivers (including the ATI Radeon GPUs) and Gallium3D enhancements.