With great startup scene, I mean there are bunch of cool startups within biking distance of each other (To name just a few http://www2.layar.com/, http://www.phusion.nl/, http://www.ebuddy.com/, http://www.supersaas.com/, http://www.guerrilla-games.com/). So you're bound to run into fellow entrepreneurs.

It also has a large number of headquarters of multinationals (Cisco, Philips, etc) so expat services are well developed.

I'm not really into generally accessible meetups myself, but I'm sure I've seen a few announcements come by of various functions.