The iconic Ariston Café in Litchfield, IL is a popular stop on Route 66 and they've opened a Route 66 museum right across the street from it. Litchfield also has one of the last remaining drive-ins on Route 66 and has classic car shows at it every year.
You might also look into Niehaus Cycles Customer Appreciate Days in Litchfield. It is generally in May. It is a HUGE gathering on motorcycles from all over everywhere. They have a beautiful parade of bikes and other activities.
Also, Country Classic cars is a fun place to stop and stretch your legs. It is a car dealership that sells nothing but classics. I love to look at those cars.