Ambient occlusion is a great way to fake indirect and significantly boost render times. I use it in combination with building a light grid, with the replicator, of bulb lights. (The bulbs in the light grid I'll have set to only .5 to 3% strength)

There is not substitute for a high fidelity Indirect lighting render, but you can get pretty close with smart AO. The payoff really comes into play if you are rendering an animation.