Hey let's go skating with the Friday Night Skate tour-group. If you don't know what is it, just go visit the web site; (http://www.fridaynightskate.com/)
In general it's 20km skating in the city of Amsterdam. I did it once and it's a lot of fun. It's free of charge. They are meeting at 20:00 at the "round bench" next to the Film museum in the Vondelpark. The event will start at 20:30 till around 22:30.
I suggest to meet up at the cafe in Vondel Park next to the Film Museum. We could meet, chat and have a drink before the skate.