BASIC stands for Beginner's All-Purpose Symbolic Instruction Code, but don't let the "Beginner's" fool you - BASIC has been used for a wide range of powerful programs, from NewsBase that many people use in conjunction with Messenger to store their emails and news, to RiscCAD, the well-liked computer aided design program.
 
BASIC has a long history - the 20-year-old BBC microcomputer started up in BASIC by default, though obviously an older version than the one that is now built into every RISC OS computer.
 
It is a simple language to learn, is very easy to get into and is remarkably quick - these have all led to a plethora of programs written in BASIC (including some of my own ).

Links

ArmSort

Module to provide easy sorting of BASIC arrays

Steve Kappa

Contains various interesting BASIC utilities, such as Basalt which provides some extensions to BASIC, and some BASIC StrongHelp manuals