I do not, as a general rule, build super light frames. If you're looking for a <3 pound frame, I'm not the guy you want. My goal is to build durable, long-lasting bikes that can be ridden for decades. That means a bit more material.
With that said, average weights for an average rider (160#) probably tend to be somewhere around:
Geared 29" mountain bike: 4#
Singlespeed (Paragon sliders) 29" mountain bike: 4.4#
Traditional road frame: 4#
Compact road frame: 3.5#
Full suspension (XC) 29" mountain bike: 7#
Full suspension (DH) mountain bike: 8#+
Obviously weights will vary all over the map depending on the size of the rider and the intended application. The lightest frame I've ever built is probably in the low 3# range (for a petite lady on the road) and the heaviest is 10#4oz, for a 400#, 7' tall gentleman who wanted to ride trails.
So there you have it. I'll make your bike as light as I can while still keeping it relatively bombproof.