Dave Ransom Software
Home of STSPLUS, the satellite tracking software used at control centers, astronaut training facilities, and on the Mir space station. Plus a ton of good space links.
http://www.dransom.com/

NORAD Two-Line Element Sets
Orbital data for any satellite tracking program, updated regularly by CelesTrak.
http://celestrak.com/NORAD/elements/

AcuSat
[commercial, demo available - Win95/98/2000] Satellite dish aiming software - Calculate azimuth and elevation coordinates for satellite dish positioning.
http://www.acusat.com

TrackingSat 2000
[commercial, demo available - Win95] A TVRO Satellite Tracking Program. Provides technical calculation that you will need to install your TVRO antenna and align it with the satellites in orbit.
http://www.geocities.com/trackingsat/index.html

Satellite Tool Kit
Full featured commercial satellite tracking software with FREE licenses for non-commercial use! Windows 9x/NT/2K/ME/ETC, Linux, SGI, Solaris and HP/UX clients available. Excellent support staff. [Ed. note: As of version 4.3 (April 2002) they converted to free distribution on CD only, the software is no longer available on line. I received my CD one week after ordering it.]
http://www.stk.com/

Satellite Tracking Software
An extensive list of satellite tracking programs and related astronomy programs for IBM, Macintosh, Unix, Amiga, and Archimedes systems.
http://www.satobs.org/orbsoft.html

PocketSat
Satellite Tracking Software for the PalmOS platform by Emm Graphics. Inexpensive shareware, and well worth it for the portability. Limited demo (5 satellites max) available for download.
http://www.bigfattail.com/pocketsat/index.html

Gnome Predict
Real time satellite tracking and orbit prediction program for Linux. Both source code and precompiled binaries available free.
http://groundstation.sourceforge.net/?gpredict

Sebastian's Home Page
Information on spaceflight topics; offers his visual satellite tracking program for Windows with screenshot.
http://www.sebastian-stabroth.de/

Nova for Windows
tracks an unlimited number of Earth-orbiting satellites in real time. It is fast, accurate, and easy to use. Nova displays satellite positions on realistic full-color maps.
http://www.nlsa.com

GLsat
Cross-platform 3D satellite visualization utility. Calculates satellites current position, and then displays their position around the Earth.
http://glsat.sourceforge.net/