I am planning on using an arcade sized hoop, nothing too fancy though. I was thinking of placing the sensor underneath the circular part of the rim. I looked into using a capacitive proximity sensor and modifying the ball so that it has thin metal strips that can be sensed. I haven't really messed around with the sensor yet since I just started trying to order parts and other things. In my mind it makes sense, but I may be way in over my head. Honestly, I just need it to work for me well during my presentations and I'll be happy.
A link to the countdown timer:
http://www.hobbytronics.co.uk/arduino-countdown-timer
Or I also found a stopwatch project:
http://arduinoprojects101.com/arduino-stopwatch/
I think the stopwatch might be a little easier to use. Any thoughts?