Australian Cycling Forums - Bicycles Network Australia

From another site:

Where: Lake Ginninderra
When: Thursday 1st April 2010
Who: Everyone is welcome. MTB, road, single speed, fixed, trikes, commuters, unicycles, cruisers, electric, etc etc
Info: Same as the last couple of years. Start (6.30pm) and finish (approx. 7.10pm) at Cycle Surgery. Entry via donation, ride at your own risk, helmets a must.
At this stage we won't be putting on a BBQ at the finish, but there is pizzy, pasta, chinese, and thai at the shoping centre if you want to hang around and chat.

Thanks - first I'd heard of this.

1 April? Sheldon always had something special on that day and maybe this is in memory of that.

Yes. His death was a couple of months before April, so it made sense to hold a memorial ride on that day.
All proceeds go to the MS society, as he had suffered from MS.

about Sheldon
Sheldonbrown.com