Looking to blur out a background to reduce distractions?  In Lightroom 3, use the adjustment brush with Sharpness at -100.   If this is not enough blur, do it again:  click on New to start a new adjustment, and paint a second time.

Also consider using the graduated filter with -100 Sharpness to simulate a shallower depth of field where the sharpness drops off gradually.   UPDATE:  If you blur out an object that you want to keep sharp, use the adjustment brush and paint back over the object with +100 Sharpness to restore its sharpness!

Is this cool, or what?

Here’s a video on how to use the adjustment brush in Lightroom.