Geographic (or Geospatial) Information Systems refers to systems used to collect, store, manage and analyze data collected through a variety of means and merged into one database. There are a number of formats in which it can be provided to users. The main formats are: digital map; Vector file; Raster file; and software file. Of these, Vector is the most widely used because of the number of options embedded in the software, which also makes it the most unwieldy. In other words, while Vector formats provide the most options for storing and manipulating data, it is not necessarily the most user-friendly. Within Vector are the Arc Export options, including ASCII, as well as AutoCAD. Digital images are often best saved using the raster formats.
Because of the rapid and continuous evolution of information technologies, it is unlikely that there will be a broad standardization of formats instituted in the foreseeable future. Procuring hardware compatible with constantly-changing software and vice versa will remain a frustrating and complicating part of life. As database and spreadsheet programs change (not necessarily improve, but certainly change), so will the formats in which data can be purchased.
Two good sources for information on GIS formats are Harvard University's Graduate School of Design GIS Manual [www.gsd.harvard.edu/gis/manual/data_structures/] and Geocomm's GISDataDepot [www.data.geocomm.com/helpdesk/formats.html]