Right now I'm thinking Tuesday the 16th, but if someone is interested and can't make it that day I could probably do another day instead.
So I propose to meet up at Voyagers just after they open around 10am on the 16th for a quick smoke, then hop on tram 26 for a ride to the Ijberg and catch the ferry at 11. If no one else is interested in checking out a 13th century castle then I'll just have to go by myself.
For more info you can check out http://www.amsterdamboatexcursion.com or Http://www.muiderslot.nl