For 5 years now (started in 02) there has been a bike run from Boston to Ground Zero.
I have gone twice. We start from the Boston area with a prayer and once in NY we gather for a short prayer at Ground Zero. On 9/8/07 they did this year's run and they are already planning next year's run. We will not forget and prayers will continue.
http://www.remember9-11ride.com/