I have been a runner for several years....always off and on, but always come back to it. I started a good training program in January 08 for my first half marathon, which will be in two weeks - the Kentucky Derby Marathon. The training has gone great and I've gotten up to my long runs without any problems. I'm thinking now I want to keep it going and train for a marathon in September. Is that too soon, or should I wait longer?

You should be fine. I did the same thing in 2006. Trained for the Cleveland half which is run in May and then continued training and ran the Akron marathon in September. I used one of the training programs I found on-line - Galloway or Higdon, can't recall which. In any event, those programs are generally 16 to 18 weeks so you should be able to time it just right. Your 1/2 training will give you a good base to jump into the full training program.

Good luck.