Sean,
In years past, there have been many parties around the neighborhood on Night Out. Some are registered, some are not. If other blocks are like ours, you won't see posts because we have direct contact with our neighbors (email and/or flyers). There's likely more parties going on that you'll see listed on various Web sites because not everyone registers their block party (this is the first year that our was registered).
If there's not a party on your block, it's not that difficult to organize one. In fact, it's one of the easiest parties you'll ever throw.
If your block isn't having a party, take a stroll around the neighborhood. My bet is that you'll see a lot. If you're not so great at sniffing out a party, head over to the 500 block of N. 71st Street and you'll find the greatest group of neighbors in the neighborhood.