Ryanair is having a special for one way flights for £1 including all tax and fees for purchase through Sunday for most routes. So far I am seeing lots of availability. Usually they run the promotion for £1 but tax adds £20-25. Make sure to select flights that say "No Taxes"
Certain forms of payment (American credit cards) are supposed to add a £4 fee.
Here are the booking rules:
Fares include taxes, fees & charges
Booking Period: Tue 30th Sep 08 - Sun 05th Oct 08
Travel Period: Wed 15th Oct 08 - Tue 16th Dec 08
Applicable Days: Mon - Thurs & Sat (subject to availability)
Flight must be purchased: 14 Days in advance
Blackout Period: 17th Oct '08 - 03rd Nov '08 to/from Edinburgh / Glasgow
24th Oct '08 - 03rd Nov '08 to/from Ireland/UK
Notes on this fare: All Holidays, School Breaks and Major Sporting Events are excluded from this offer
www.ryanair.com