This weekend, the NYRR has one of their supported long-distance runs, ranging from 6 to 20 miles in Central Park. These runs are especially great if you don't have anyone to do long runs with and/or want to set a certain pace. These are a little earlier in the season than previous years, though there are plenty of halfs (or longer) to help in your marathon preparation. I seem to recall paying $5 to $7 for them - if you haven't signed up, though, it'll cost you $15 for race-day registration (and you don't even get a T-shirt!) The next one is Aug. 1.
There's also a race in Central Park on Saturday, a 5K, for those interested.
Here's an admittedly incomplete list of some upcoming races:
July 11, Ladder 5 5K, (XC)