I'll start with the same disclaimer as the last 26.2 Questions post. I'm not a coach. I'm not certified in anything. I'm just a dude who has run a few marathons, read a few books about running, and read several distance running periodicals. Consult a coach and a doctor before taking my advice to heart. After all, I'm sidelined with a stress fracture, so I obviously don't know everything.
One of the questions that came up often during the long runs is "What should be my next goal after the Rocket City Marathon?" That is an excellent question!
First and foremost... For the first two weeks after the marathon, you should do as little running as you can stand. Take off if you want. Run very easy if you want, but don't run much and don't run far. You cannot run too easy or too little during the first two weeks after the marathon. Recover. Running 26.2 miles is a lot to ask of your body. Now, give your body a break.
Ok... After you've recovered, then what?
Whatever you do, please keep running! Don't just check 26.2 off your bucket list. Running has completely changed my life. Running draws me closer to God by giving me time with nature and time to pray alone. Running has introduced me to so many great people and gives me opportunity to spend time with them on the roads and trails. Running has helped me to maintain a healthy weight. Running has helped me in my battle with depression. Running will reward you.
One good option for a next step is to leverage this huge base that you have and run some shorter races much faster than you ever thought you'd be able to. The 26.2 program is very good because it introduces you to all types of running. There are easy runs. There are track workouts. There are tempo runs. And, of course, there are long runs. Once you ease back into running, experience with those different types of running will serve you well. Once you're running comfortably again, hit the track and do some intervals. Check the Fleet Feet Calendar and pick out a goal race and consult a coach for a training plan. There are plenty of races in the Huntsville area to choose from. With the 26.2 base, you can be ready to run a fast 5k in about 6-10 weeks.
Some have asked, "Why don't I just run another marathon while I'm in shape to run a marathon?" If Rocket City was your first marathon, I strongly discourage you from running another marathon until next fall at the earliest. Sure, you can run another marathon soon, but it's just not ideal.
Others have asked, "What about my long runs? Do I keep doing them?" A long run is definitely a staple of any fit runner. However, there are long runs and then there are marathon training long runs. If you're not training for a marathon, then you really don't need to run 18+ miles. You can get similar benefits and recover faster from a weekend long run of 12-15 miles. I'd recommend that you keep a "long run" in your weekly schedule of about that distance. It'll do you good.
Hope this helps! If you have more questions, ask and I'll try to answer.