Leadership:  None declared
Activities: Al-Qaeda appears to have infiltrated a number of Mosques in Germany, some of whose members plotted and prepared for the 9/11 attacks in the U.S..  In addition, European Al-Qaeda members or "wanna-bes", funded by Pakistani Jihadists, appeared to have planned and carried out the sttacks on the London mass transit system (2 separate occurances). Some U.K. officials believe the Al Qaeda links are tenuous at best, citing the Pakistani Jihadists as acting as "lone wolves" with funding from home (Pakistan MIJs)  Evidence in the trials of the Madrid, Spain train bombers also point to Al-Qaeda links in both the planning and actual attacks.  It is not clear in the Spanish case, however if the attackers were members of Al-Qaeda or just "wanna-bes" however, later statements by Osama bin-Laden appear to name Al-Qaeda and take credit.  There is also suspicion that Al-Qaeda members are whipping up French Muslim youth on an annual car burning and rioting.
External Aid:  Unknown but suspicions of Pakistani Jihadist funds (trials of subway bombers in U.K.)
Strength:  Perhaps a few hundred in all of Europe however France's multi-million population of disfranchised Mulsims may harbor many thousands of sympathizers.
Links:  Al-Qaeda, and numerous Pakistani Jihadist groups (U.K. especially)