Extensive Belgian MTB site with a full race schedule:
http://www.mountainbike.be

Belgian Mountain Bikers Forum:
http://www.b-m-b.be

Brussels International Group of Mountainbikers:
http://www.bigm.be

GPS mtb trails in Belgium:
http://www.wikiloc.com/trails/mountain-biking/belgium

GPS rental for tourists:
http://www.opt.be/contenus/mountain_bike_and_gps_in_east_belgium/en/3240...