SpatiaLite!

PostGIS adds support for geographic objects to the PostgreSQL object-relational database. In effect, PostGIS "spatially enables" the PostgreSQL server, allowing it to be used as a backend spatial database for geographic information systems (GIS), much like ESRIs SDE or Oracles Spatial extension. PostGIS follows the OpenGIS "Simple Features Specification for SQL" and has been certified as compliant with the "Types and Functions" profile.

A location intelligence and visualization engine that empowers you to effortlessly transform data into insights. With CartoDB, connect and map location data, quickly customize your visualizations, and develop powerful location based apps.

H2GIS is a spatial extension of the H2 Database Engine in the spirit of PostGIS . It adds support for managing spatial features and operations including a Geometry constraints, the Open Geospatial Consortium (OGC) Simple Features for SQL (SFSQL) functions and additional spatial functions that we (the OrbisGIS team) develop.