Compass rose from the Catalan Atlas by Cresques ben Abraham, 1375 (image via Wikipedia).
A control point marker used in orienteering (image by Leinad, via Wikimedia Commons).
ArcGIS is just one of many GIS tools available. Here are some additional resources for exploring and using GIS:
Teach GIS – A site devoted to finding resources for teachers (and learners!) of GIS.
GRASS – Originally developed by a branch of the US Army Corps of Engineers, GRASS is a free GIS software available for a variety of OS platforms, including the Windows, MacIntosh, and Linux environments.
Quantum GIS – QGIS is another good open-source GIS software, offering an array of functionalities across multiple platforms.
OpenStreetMap – OpenStreetMap is a handy open-licence basemap for Internet-based map displays.
BatchGeo – BatchGeo is a GIS interface for working with and displaying tabular geospatial data.
Python – Python is an open-source scripting language that can be used to customise and automate geoprocessing operations within ArcMap. See also:
Computer Science Circles Python tutorial
Python Geospatial Development (available for online perusal through myneu)
Open Source GIS – This is a very thorough guide to an impressive array of open-source GIS softwares and tools.
This list is by no means all-inclusive. If you have a site to suggest please let us know!