Mesa 7.7 delivers on VMware's virtual Gallium3D driver (the SVGA driver) that allows for Gallium3D to be used on their virtualization platform, several new OpenGL extensions, major improvements to the ATI R300 Gallium3D driver (named "r300g"), and a new Mesa texture/surface format infrastructure.
The new VMware Gallium3D driver depends upon new DRM code that can be found in the Linux 2.6.33 kernel and later.
New OpenGL extensions in Mesa 7.7 include GL_ARB_draw_elements_base_vertex, GL_ARB_depth_clamp, GL_NV_depth_clamp, and GL_ARB_provoking_vertex.
Mesa 7.6.1 simply provides a collection of bug fixes since the release of Mesa 7.6 in late September.
While Mesa 7.7 now provides a more recent snapshot of the latest and greatest code for this OpenGL implementation and open-source 3D drivers, there are already features piling up for Mesa 7.8. Mesa 7.8 should be released in the first half of 2010 and will feature improved geometry shaders, Gallium3D state tracker improvements, many core improvements to Gallium3D, R600 OpenGL 2.0 / GLSL support, and many other driver improvements for classic Mesa and Gallium3D.
The joint Mesa 7.6.1 / 7.7.0 release announcement can be found on the mailing list.