What are some good websites/apis built using government data? AFAIK, most countries have started publishing open datasets about things such as weather, transpor

What are some good websites/apis built using government data? AFAIK, most countries have started publishing open datasets about things such as weather, transportation, politician backgrounds, even law! But I've yet to see some useful websites/apis built on top of them. Most are related to politics, visualization and/or research (which is a laudable enough but doesn't make them worth checking regularly).