Towards the beginning of this year we reported on hybrid graphics support for Linux coming in a crude form via something David Airlie calls "vga_switcheroo", which has since been integrated into the mainline Linux kernel and related components. This allows for a rather basic and rudimentary way to switch between two graphics processors, but it requires shutting down the X.Org Server and is far from being a streamlined experience. It evolved quickly at first to the point that it supported delayed GPU switching, but lately has not received much attention. Hybrid graphics support under Linux is far from being close to the same level of the experience notebook users have when running Microsoft Windows 7.
We also reported on initial open-source multi-GPU rendering support via some other David Airlie work called PRIME, but that too hasn't seen much love in recent months. NVIDIA has also confirmed that their Optimus technology will not come to Linux.
About all that's new in the way of developments is a new kernel module called acpi_call, which allows those owners of notebooks with dual graphics processors to try out different ACPI methods for switching on and off the discrete GPU. While you may be able to figure out the ACPI call needed to switch off the GPU, support for automatically placing that call to either turn on or off that GPU when needed, is not yet in place.
Those interested in trying out the acpi_call module or other hybrid graphics experiments under Linux can find a few more details on this blog.