I saw this idea a while ago and thought it looked like fun. Later when I found pool noodles at the dollar store I had no excuse.
To make the race track I took my pool noodle and cut it in half. I found that a serrated knife made a much cleaner cut than a regular knife. I then used toothpicks to secure each half of the noodle side by side.
And a finish.
Don't forget to put something at the bottom of the track to catch all your marbles.