This page is basically a repository for interesting / useful datasets.
In the UK, the police.uk website provides facilities for mapping monthly street-level crime data. There is also a data download facility
The National Geospatial-Intelligence Agency (NGIA) have a big database on anti-shipping (piracy) locations.
LeedsDataMill has some footfall data for certain points in Leeds:
LandScan Population Estimates
LandScan data are worldwide estimates of average daily population densities at a spatial resolution of ~1km2.
The UoL Library has recently purchased data for the UK, available here.
- The NaN group has a repository of public data that they use for modelling complex systems. Includes data covering Twitter, web traffic, social bookmarking, etc.