Enterprises, scientists and amateurs world-wide are using geodata for all kinds of projects. At worst, it is used for those annoying geolocation analyses on web pages which present regional advertising - or even a bad web page translation - based on the location of the IP address. Most internet users have more fun with the many forms of presenting Google Maps data. Incidentally, Google Maps isn't all that "free" but rather "freely accessible up to a point" in strict licensing terms. This also applies to other "geo services". So where can we find a freely licensed "world"?
A first access point is FreeGIS.org. Apart from a number of applications and various "Geo APIs" for all kinds of programming languages, it contains comprehensive lists with sets of all kinds of geodata. A lot of it originates from Nasa's Visible Earth Project, but you can, for example, also find a US road atlas by open source protagonist Bruce Perens, data for the city of Osnabrück or data about European waterways.
Incidentally, Canada has set a good example and has released geo and weather data collected for public institutions free for non-commercial use on GeoGratis.ca since last April. Long term geo mash-up enthusiasts should read the OpenGeoData blog which has collected links and information about freely available geodata for two years - interested amateurs need to rely even more on link collections to the data scattered all over the globe because there is no central global database.
So what can be done with the data? Even minimal programming skills are enough to develop ideas for numerous projects and make finished projects available to everyone under free licenses. The most important project of this kind is Wikipedia's georeferencing project, which endeavours to attach latitude and longitude references to any even slightly geographically relevant article containing some place on Earth. Numerous visualisations can be generated from these references. OpenStreetMap is another free project which works like Google Maps but can be edited, and therefore expanded, by users.