In the past, for the most cases I relied on Google Maps and metadata they provide. I knew about other similar services, including specific for certain countries, but I’ve never brought my close attention to them.
At that time I have never heard of openstreetmap and anything related to it. Then few years ago it was used in one prototype application ( hi, Daniel! ) to store map data and tiles on iOS device to be able to access it
offline. This was very interesting experience.

According to the official page on OpenStreetMap web-site, it was founded in 2004 by Steve Coast. Main motivation to start open initiative came from imposed restrictions for data editing, because majority of map vendors
at that time provided proprietary map data. Over the time it grew bigger and in 2006 (after two years) it evolved into OpenStreetMap Foundation with around 3000 of active contributors. Nowadays, number of contributors
is around 1 million people from all over the world.

There are number of commercial projects and companies which uses OpenStreetMap:

• Foursquare
• Flickr – for cities, where proprietary map data is not available or not accurate enough
• Mapbox – alternative to Google Maps
• Wikipedia
• Apple Inc. – iPhoto for iOS, map data that is not available from TomTom

In my personal opinion, story of openstreetmap is quite inspiring. It started as something very small and simple and evolved into a big project with a large number of contributors.
As a result, people themselves responsible for data accuracy and quality. Combined with contributions from local government or business it is possible to achieve a state of accurate and up-to-date data quality.
If you like to use data or contribute to the project, you can start from here: http://wiki.openstreetmap.org/wiki/Main_Page