I'm doing a project in cycles and I want to render it but its too slow on my CPU. So I want to render the scene in luxrender but without starting the project all over again.
Luxrender in version 1.6 (latest iteration) offers a basic material converter. Check out the release notes on the Luxrender Site here (scroll down to the last entry): http://www.luxrender.net/wiki/New_in_1-6
The button to convert all materials is in the render tab:
to convert elements individually, do a space bar search in the 3D viewport. Hit Space and enter 'convert' gives you these functions:
Disclaimer: If this makes your renderings FASTER I'm not sure. It depends on the scene and the aim. But it gives you a quicker starting point.