This page provides a list of good places to find shapefiles or other geographic information. It also provides a list of tools which can be used for GIS ETL.
Sources of Data:
- GADM - World administrative boundaries. Countries and lower level subdivisions.
- Natural Earth Data - Huge set of shapefiles for natural features as well as administrative boundaries (and more).
Fairly low-res even at its most detailed.
- GeoNames - Loads of data for lots of different countries. Our postcode GeoPacks mostly come from here.
- Map Cruzin - A repository for a huge amount of geographic data. Shapefiles are generated from OSM data.
- QGIS - Open source GIS software. Can load shapefiles (and other formats), can edit files and convert between formats (haven't had much luck saving WKT, though). Also has some plugins for vector operations, so can be used for simplifcation.
- OpenJUMP - More open source GIS software. Occasionally has problems reading shapefiles.
- mapshaper - Brilliant, web based tool for simplifying shapefiles.
- FWTools - Popular open source GIS toolkit. ogr2ogr is probably what you'll be most interested in. Allows you to convert between formats (you will pull your hair out trying to convert to csv, so give that a miss). THE tool for when you need to change a projection.
- JTS Topology Suite - A great Java geometry library. For when none of the available tools meet your needs and you have to roll your own.
Related article/s: The GeoPack creation process