Love them or hate them Ryanair changed the way Europe travels. They now serve over 205 destinations and despite a few recent issues are one of the most on time and reliable airlines out there. Not to mention cheapest.
Presumably the recent pilot issues are behind this extended sale but they are offering a different deal a day until next Monday for flights in January.
A quick search today shows some real bargains. Dublin to London return for under €10 with respectable flight times. At that price you can even splash out and reserve a seat for €2.00.
Loads of routes are available so have a look, these prices almost make me want to move back to Europe.