Where can I learn more about LTE coverage and build out schedules in the US?
Not much in the way of a major community database of real-world speeds, sadly. Here are some other resources:


Verizon's LTE coverage map
AT&amp;T's HSPA+ coverage map (and overview)
Overview of all major carriers, and another (older)
More general information on current/planned deployments
Verizon coverage map with speed tests - Minneapolis/St. Paul area only.


You might also use the FCC's GIS data to find out more about what towers already exist.  Presumably, they're not going to build new towers for LTE - just add antennae to existing sites.