It would be hard to overestimate the impact of computers and software on the science and hobby of astronomy. On the amateur level, astronomical software, along with CCD cameras, permit amateur astronomers to conduct observations only possible at large professional observatories a decade or two ago. Software, either in a computer on in an onboard chip in digital setting circles have revolutionized our hobby. Here are some resources for the best in astronomical software.
BASIC Programs
Downloadable astronomy programs (in BASIC) from Sky & Telescope articles.
JavaScript Utilities from Sky & Telescope
Use these handy routines to find Jupiter and Saturn's brightest moons, locate Jupiter's Great Red Spot, determine the times of Algol's minimum brightness, and more.