Montgomery to Yorkville is a great 10 mile paddle on the fox river. You start at the dam at Mongtomery, then take out at the dam in yorkville. It takes you past Oswego, then through a chain of islands.
This stretch takes 2-4 hours, depend on current. At my best, I've done it in 2. If it's a casual time, it can take closer to 4.
Metamorphosing from an average camper into a true outdoorsman