Spatial Data Resources
ArcGIS for UC ANR owned computers free of charge
ArcGIS is also commonly free or deeply discounted for students through your local college or university. A free 60-day trial version of ArcGIS can also be obtained through Esri here.
Quantum GIS is an outstanding free and open source GIS software.
(Note: The 64 bit Windows version of QGIS can occasionally be more glitchy than the 32 bit version, even on a 64 bit computer)
For a good introduction to using QGIS, check out the QGIS Tutorial by Nate Roth
Google Earth Pro is an extremely useful and easy to use platform to locate and map features anywhere on Earth and is now free to download and install on your computer.
DNR GPS is an outstanding program for processing GPS data, provided for free by the Minnesota Department of Natural Resources.
CartoDB is an excellent online service for developing and hosting online maps.
General Geospatial Data
Land Cover and Wildlife Habitat
Weather and Climate Data
Worldclim (Current, past, and present interpolated global climate data sets)
CIMIS (Weather station data)
USGS Earth Explorer - Hosts a wide variety of imagery, including Landsat and air photos, as well as digital elevation data
ArcGIS Coverages (from the California Department of Fish and Wildlife)
GeoTIFF and SID (from the former California Spatial Library - CaSIL)
MASTER (NASA’s Airborne ASTER/MODIS simulator)