The Carmel Marathon is a great race for those looking to fill a calendar. It's not really a destination race, but it's well-rounded. The expo is fairly large, with plenty of booth featuring races and runner gear and the race shirt gets better and better each year, as well as the medal. I've run this race twice and enjoyed it both years.
The course winds through residential Carmel, past some beautiful houses and down the Monon Trail footpath. Aid stations are well-manned and there is plenty of spectators along the course to keep you motivated. Parking near the start/finish is ok since they finished the parking garage nearby, however for the years I ran it, they used shuttle buses to supply runners with parking places offsite.
All in all, it's a well designed race and I would run it again.