How can I hook up 2 1500 watt power inverters to produce 3000 watts

Need more information. Is this going to a single 3000 watt load? How is this being used?

In general, no. Can't say for sure that there exists some that can though Xantrex Technology Inc. makes stae of the art stuff, so I would start there.

Some generators, such as those mamde by Honda have the capability to be paralled. It requires both output cables and a control cable. If I understand the control scheme correctly, one device would use a reference as the input and the other would use a divided down version of the output of the first device. This makes the first second device add current to the output, otherwise the power supplies would fight and the strongest one would win The other would let out the magic smoke and won't work anymore.