www.iamsterdam.com, a very informational site about everything one needs to know when visiting Amsterdam
www.gvb.nl, public transport in Amsterdam
www.rijksmuseum.nl, buy your tickets for the Rijksmuseum before you queue up
www.vangoghmuseum.nl, buy your tickets for the Van Gogh Museum beforehand
www.annefrank.org, the house where Anne Frank used to live during WW II