I stumbled upon a neat mashup that Steven Nikkel put together. It's neat to see where the cell towers are and which bands they handle.
What usually happens when I've been out in the woods while ATV'ing, we'll stop and we'll find that we have picked up the odd signal from a tower and a few text messages have come in. This might not sound like a big deal, but I'm talking about about locations that are so far from the official dead zone that it's pretty cool to find these odd locations that do make contact with a tower.
Next ATV trip I'm going to try figuring out where more sweet spots are in case of emergency. I'll have to admit, this may end up being a fun and geeky hobby.