One person's terrorist is another's freedom fighter.
Al-Qaeda
Probably the most infamous terrorist oranisation in the 21st century world, their leader Osama bin Laden is susposedly responsible for organising such attacks as those on September 11 2001, the 1998 Embassy bombings in Kenya and Tanzania and the attack on USS Cole. The origins of the Al-Qaeda organisation date back to the 1980s. Osama bin Laden, like many Muslims, was eager to support the Afghan forces that were resisting the occupation of Afghanistan by the Union of Soviet Socialist Republics (USSR), which had invaded in 1979. With money he had inherited, bin Laden was able to finance anti-Soviet resistance in Afghanistan, recruiting Arab volunteers to fight for the cause, even sometimes leading them into battle.
Useful links
Inside Al-qaeda
terrorismfiles.org : al-Qa'ida (al-Qaeda)
September 11 2001
BBc News - Investigating al-Qaeda
KADEK
KADEK were formerly know as the PKK or the Kurdistan Workers' Party.
Uselful links
TERRORISM WEB SITE - FORSNET
BBC News - KADEK
IRA
IRA stands for Irish Republican Army
Useful links
Terrorism Q&A | Irish Republican Army (UK, Seperatists)
BBC News - Provisional IRA
ETA
Useful links
Terrorism Q&A | Basque Fatherland and Liberty (Spain, separatists) 2
BBC News - Who are ETA?