The GIMP is the GNU Image Manipulation Program, a freely distributed piece of software suitable for such tasks as photo retouching, image composition and image authoring, similar to Adobe Photoshop, but running on X Window system on Unix/Linux platforms.
Good Starters at TeX Users Group.
A wonderful LaTeX manual in NASA.
Debian is a free, or Open Source, operating system (OS).
On www.wolfram.com, the creator of Mathematica.
MathWorld is a convenient, comprehensive, and interactive mathematics encyclopedia intended for students, educators, math enthusiasts, and researchers. Like the vibrant and constantly evolving discipline of mathematics, this site is continuously updated to include new material and incorporate new discoveries.
On www.mathworks.com, the developer of Matlab.
On-line version of Martin V. Zombeck's Handbook of Space Astronomy &s; Astrophysics.
Physical Reference Data at National Institute of Standards and Technology.
GNU Manuals on Free Software Foundation site www.gnu.org.
The default email reader on most NYU systems (SCIRES, IS, ...).
Searches for man pages on many Unix-like systems (BSD, Linux, Unix, ULTRIX etc).