In the past it has taken AMD months to implement support for new OpenGL specifications within their proprietary Linux driver, but this time around they're with it and it's coming just a few days after NVIDIA released an OpenGL 3.3 Linux driver. NVIDIA has yet to release an OpenGL 4.0 Linux driver, but that's because they don't yet have any DirectX 11.0 / OpenGL 4.0 compatible hardware, but that will come any day now with the introduction of the GeForce 400 "Fermi" graphics cards.
The OpenGL 4.0 specification was just released earlier this month at the Game Developers Conference with some huge and long-awaited changes to this open graphics API. OpenGL 3.3 was released at the same time and it seeks to bring back as much OpenGL 4.0 functionality to OpenGL 3.x hardware (DirectX 10.x GPUs).
The OpenGL 3.3 support found in this just-released Catalyst driver covers all Radeon / FireGL / FirePro GPUs, which goes back to the Radeon HD 2000 series. The OpenGL 4.0 support is limited to their Radeon HD 5000 series (R800 / Evergreen) ASICs. This preview Linux driver is coming at the same time as AMD releases their Windows XP and Windows Vista / 7 drivers.
While this preview driver goes without official support, it can be found on this web page for those wanting to experience OpenGL 3.3 / 4.0 support. This Linux driver carries a fglrx 8.712.3.1 version string.