ToplapSystems

Languages for For Live Coding. The ones with community links are probably a good place for beginners.

Textual languages

SuperCollider (community | examples) - C and smalltalk based language, for live coding sound synthesis and musical patterns via JITLib and GraphicsSpace
ChucK (community) - strongly timed on-the-fly language featuring the Audicle and miniAudicle
fluxus (community | examples)- Scheme based, centres around game engine, primarily for VJing but has a secret synthesiser
Impromptu (community | examples)
redFrik
packet forth
musique littérale, built with Quoth, in turn built with Squeak
noisepattern (part of http://www.pawfal.org/Software/livenoisetools/ )
Ruby(druby,irb,rjb) | JSyn (Client-Server)
Hyperyarn
Flaxus, Toplap flash based application
SSCLib built with SuperCollider for live slow coding
Circa+Plastic
oflivecoding - Environment for live coding in javascript within the c++ openframeworks toolkit.
ixi lang - A high level live coding language built on top of SuperCollider. More info on the ixilang page.
field - A hybrid development environment for making digital art
context free music language (cfml) - a library/sublanguage for Impromptu
Extempore - A live-coding environment which borrows a core foundation from the Impromptu environment
live-processing - A Processing clone with livecode capabilities.
Overtone - An open source audio environment on Clojure.
Conductive - a library for Haskell
Music-As-Data - An open source language for live programming music in Clojure

The Thingee + ThingeeLanguage
betablocker
Al-Jazari (refused TOPLAP approval, entering third tribunal at dynamic high court)
TOPLAPapp:an iPhone/iPod Touch live coding musical puzzle game
Text - A visual language based on Haskell