For what it's worth, I found this list. Some of these don't really fall under 'low cost' category and some have already gone under, but it does show that there are a fair number still out there.
Aegean Airlines
Aer Arann
Aer Lingus
Air Berlin
Air Italy
Air Malta
Arkefly
Avro (charter)
blu-express
Blue Air
bmibaby
BritishJet
Brussels Airlines
Cimber Sterling
Condor
Corendon
Easyjet
First Choice
Fly baboo
Flybe
flythomascook
Germania Express
Germanwings
Hifly
Iceland Express
Jet2
Meridiana
Monarch
MyAir
MyTravel Lite
Norwegian Air Shuttle
Onur Air
Pegasus Airlines
Ryanair
Sky Europe
SmartWings
SunExpress
Swedline
Thomsonfly
transavia
TUIfly
Vueling Airlines
Wind Jet
Wizz Air