Spectrum Nerd (spectrumnerd.com)

I'm not so sure this is actually "available" spectrum, as it is unused-by-carrier spectrum.

For example: the large dark spot in New Mexico is probably that way for a reason: The VLA is smack in the middle.

Very neat visualization! Note that these charts are of static allocations, not dynamic usage. Dynamically, we use very little of the spectrum that we've statistically allocated, even in a busy urban environment: http://www.sharedspectrum.com/wp-content/uploads/2010_0923-G... (see Figure 9 for the punchline). Look at all that open real estate, and think about how much we've managed to do with a measly 100 MHz in the ISM band.