I read an interesting proposal years ago that involved using heat from data centers to warm peoples' homes. I'm not sure exactly how it would work, but it did sound intriguing.

There really needs to be more work done to figure out how we can capture waste heat on both small and large scales to help with power generation. It may not be practical in all instances, but there are probably plenty of cases where it could make a discernible difference. Some scientists are already looking into it.