Free GIS Data & Resources

Utilities

QGIS - Free, open source GIS software

ESRI's ArcExplorer is a free program to use to view GIS data

Minnesota Deptartment of Natural Resources Garmin Data Formatter

EasyGPS
Transfer files between your GPS unit and computer

Data

Florida:
Florida Department of Environmental Protection's GeoData Directory
Lots of accurate and basemap layers with very well managed metadata

FDEP's Map Direct (Internet Explorer only)
Interactive internet mapping application with DEP's GIS data

FDEP's Land And Boundary INformation System ("LABINS")
Orthophoto imagery, raster basemaps, Digital Elevation Models (DEMS), and other high resolution imagery and surveying data for the state of Florida.

Florida Department of Transportation Aerial Photography
High resolution historical imagery of Florida

FDOT's GIS Directory
Florida traffic information & transportation networks

Florida Geographic Data Library (FGDL)
Lots of Florida data (statewide, or by county), but much of it is antiquated.  I'd look at FDEP's Geodata Directory first.


Beyond Florida:
Geodata.gov - Geospatial One Stop
Browse US maps & data

MIT's Geodata Repository
Use the navigation on the left to browse through lists of US nationwide, statewide, and worldwide datasets

Stanford University Libraries & Academic Information Resources
Marine Biology GIS Data

GPSFileDepot.com Garmin GPS Maps
Browse for a number of useful layers

Harvard Geospatial Library


Bathymetry:
NOAA's National Geophysical Data Center
Maps & Scanned Images
U.S. Coastal Relief Models

Training & Tutorials

ITT Visual Information Solutions' ENVI tutorials