web links

Automatically retrieves data for your current Arcmap work frame from the following online sources

Entire country at 1:250k, select areas at 1:50k. Geology themes on INEGI base maps in PDF format. These maps could be saved to high res TIF or JPG and georeferenced into a GIS as a reference layer. The datum is ITRF which aligns extremely closely to WGS84 (they're identical for these purposes).

Free imagery archive with primarily Landsat and MODIS data, some ASTER imagery.

Besides providing medium and high resolution imagery for many parts of the earth, Google Earth can now render custom texture-mapped objects in geographical space. GoogleEarth imagery can be captured and georeferenced for later use in a GIS package like ArcGIS. I have posted instructions on an expedient way to bring GE imagery into your ArcGIS project.

Java viewer for marine and terrestrial topographic data. High res bathymetry data and SRTM data (90m worldwide, voids unfilled) can easily be viewed and saved as a GeoTIFF. These data can be brought directly into a GIS.

Orthophotos, tabular data, and other products from INEGI.

Digital Elevation Model data at with near worldwide coverage at 90m resolution based on the SRTM topographic dataset from NASA. The CGIAR people have filled the voids and are serving the data in GeoTIFF or ArcInfo ASCII format.

USGS Java viewer for browsing available datasets including Landsat, ASTER, and MODIS imagery. ASTER 1a images can also be processed into 30m DEM files, one of the best sources of free DEM data (for education and research) with worldwide coverage. You can cycle through the cloudy images by right-clicking and choosing "Send to Back". With ASTER imagery, note the ID# (L1A) of an image to order it from the EOS Data Gateway.