I saw this on a few otherblogs and thought it was an interesting idea (and I think I have done it before as well, but used the first sentence of the first post of the month).
Here, for your amusement, the first sentence of the last post of the month, 2006:
Jan: ... sure, some might say it's getting down to the wire here, but I say I'm just gettin' this party started!
Feb: What a rush it has been... I'm not ready to let go of love month just yet.
Mar: It seems my April fool's has begun a little early.
April: Sitting at the end of my peanut butter and jam packed weekend, wishing there was some way of injecting just a few more hours into it... not believing that it's over already.
May: The Goddesses Gathered for the second time, at the lovely home/studio of Goddess Siren
June: Hotels I have worked in Honey I call my love Hungry for some free timeto Hang out away from here Hardly just beginning Humming a Happy tune Harmony in all things Hugely indebted to you
July: Oh, am I ever a grumpy back-to-work person today, on a Monday of all days.
August: ... so, um, what do you do when you get to the bottom? (Learning to pole dance)
September: Another Friday, another good mood!
October: Update(d) Update Pumpkin: Purchased, yet not carved
November: I love getting Henna'd