Ok, so I have been pouring over the posts about starting problems and have not been able to put together a diagnostic strategy for my problem. Over the past several days, the dome lights occasionally would not come on and the truck would not start--I can hear the fuel pump, and it doesn't seem to be a passkey problem (the engine doesn't turn over at all, just a single click). This morning my wife and I ran a few errands, which resulted in starting and shutting off several times. No problems whatsoever. After we got home and had been home for about an hour, I went out to start my blazer and got nothing. However, the dome lights were all on, no blinking security telltale (at least not beyond a few seconds). While I didn't think it was the battery, I took it to the auto parts store, where it checked out ok (~12.5 amps, 715 CCA (rated at 700 CCA)). I did read in one of the posts that there could be a cracked plate and the battery would still show full charge. I'm not sure if they checked it with a load test.

A couple other things. It was pretty rainy here this morning when we went on errands. But I have had this truck for several months and it has seen lots of rain in that time.

Other than having the battery checked, I haven't done much else except make sure the connections were relatively clean and tight. The battery itself is stamped 2009, so it is pretty new (a Duralast Gold, I think). I can hear the fuel pump come on when I turn the key and a single click, but no crank or turn over on the engine. I have seen that it could be an ignition switch, or perhaps a starter issue, but wanted more information about where to start.

Figures that the weather is forecasted to be in the negative digits for the next couple of day! Help, please!!

 

Seems like possibly the ignition switch. A few members here have had luck getting past this issue by releasing the key slowly from the start position.
If that doesn't work, get your test light out, crawl under the truck while your wife trys to start it and test to see if you have power to the starter when the key is turned. If no power check the starter signal coming out of the ignition switch.