We'll be switching to Pajamas Media for advertising around October 1, but in the meantime you still have a chance to get a couple of weeks' worth of relatively inexpensive advertising, should you be so inclined. Just go here to buy a premium ad or here to buy a standard ad.
We get, according to blogads, traffic of either 158,000 or 177,000 per week; for some reason, it gives us different numbers for the premium and the standard options -- I have no idea why -- but in any event that's quite a few eyeballs.
Without seeing the exact prices, the usual reason for that kind of price structure is that the spot price is expected to rise. Lock in your three month rate now, or take a risk that the month to month rate won't sharply rise by even more in month 2 or 3.