The 25-year-old midfielder started his career at Grimsby Town before moving to Everton for £1.5m in 1997.
A £1m move to Sunderland followed two years later and he has also spent time on loan at Barnsley and back at Grimsby.
The Welsh international is expected to go straight into the Leeds side tomorrow and bring some much-needed attacking creativity to the midfield.
His month-long loan means he will be available for the next six games.