The FCC has released an excellent map showing 3G coverage around the country (you can see it here). Above is a screenshot of northern New England: the black places are elegible for the Mobility Fund Phase 1 - federal subsidies to get coverage in uncovered areas.
Most of the dark areas are unsurprising: northern Maine, Coos County, the center of the White Mountains, Hogback Mountain in southern Vermont - places where terrain blocks signals and makes it expensive to build towers, and there aren't many potential customers to lure phone companies.
But notice to archipelago of black in northwestern Hillsborough County and neighboring counties of N.H. That's roughly around Pillsbury State Park, part of a low ridgeline which holds Lempster Mountain Wind Farm; it appears to cover a number of small towns, like Goshen, Marlow and Windsor. This is an also an area that lacks wired broadband, one of the target locations for the Network New Hampshire Now project.
Considering that the location is barely an hour's drive from Manchester and has terrain which isn't exactly mountainous - Mount Sunapee is about as rugged as it gets - it's a little surprising how overlooked it is.
If we start feeling sorry for ourselves, however, we can go back to the FCC map and check the Rocky Mountain states. At least half of Idaho lacks 3G coverage.