Optimus, the NVIDIA technology that's becoming found on an increasing number of notebooks as a means of dynamically enabling a discrete GPU on the notebook for maximum performance only when needed and to be turned off otherwise to conserve power, has been troubling on Linux since its inception. NVIDIA doesn't officially support Optimus under Linux, so the Linux development community is left to do what they can to support this growingly-popular feature.
Some work on this front has been the experimental PRIME GPU offloading work, GPU hot-switching for X.Org, VGA Switcheroo, and some work in the Nouveau land towards Optimus support. There's also been the prime-ng / Bumblebee project that strives for this notebook technology support.
The Bumblebee 3.0 release comes after two months of development. This new release has been re-written in C and it also now features automatic power management support "out of the box" (bbswitch and vga_switcheroo power management for Nouveau driver), better configuration support, more proper system integration, and other changes. The highlights are talked about in the Bumblebee 3.0 release notes.
There's also additional details on the Bumblebee 3.0 release from the Linux Hybrid Graphics Blogspot. Packages of Bumblebee 3.0 for Ubuntu, Debian, Mandriva, and Arch Linux are currently available.
The Bumblebee implementation tries to copy how NVIDIA Optimus works under Linux with regards to using the dedicated GPU just for rendering. With this new release, there's now the much-needed power management support too. Bumblebee is implemented by creating a separate X.Org Server as a fake environment and then is called to do the OpenGL work via VirtualGL as basically a remote server.
Along with Bumblebee, there still is the fork of Bumblebee known as Ironhide -- with the same goal of NVIDIA Optimus on Linux -- that was done by one of the former Bumblebee developers.