WP7 Root Tools reports that if you are the brave sort, you do not have to wait for an official Windows Phone 7.8 update to be pushed to your phone, as Custom ROMs for multiple handsets, including the popular Nokia Lumia 800, is available on XDA-Developers already.

The build number of these ROMs are 8858 and the build tag "WM7_Main_Ship" , is believed to be the final Release to Manufacturers version of the ROM.

ROMs are available for the HTC Titan,HTC Mozart,HTC HD2,HTC Radar,HTC HD7,Samsung Omnia7,HTC Trophy,HTC 7Pro,Nokia Lumia 710 and Nokia Lumia 800 and needs an HSPL bootloader installed to be flashed.

The ROMs vary in feature list but all have at least:

Full unlock v4 – now with root access notifications.

Ringtones from your personal music collection.

Clock tile.

High quality WP7.8-compatible tiles.

USB2Video driver.

XAP deployer built in.

Windows Mobile Device Center Launcher.

Of course flashing a Custom ROM is a lot more risky that waiting for an official update, and will result in your data being lost, so its not recommended, but it is nice to know the option is there for those that just cant wait.