Graham Turner is the longest serving manager of all the clubs in League Two. The Hereford United supremo has been in charge since 1995.
This list comes from a post on the Football Forum:
Hereford ------------ Graham Turner (Aug-95)
Accrington Stanley -- John Coleman (May-99)
Wrexham ------------- Denis Smith (Oct-01)
Darlington ---------- David Hodgson (Oct-03)
Rochdale ------------ Steve Parkin (Dec-03)
Boston United ------- Steve Evans (Mar-04)
Barnet -------------- Paul Fairclough (Mar-04)
Macclesfield Town --- Brian Horton (Apr-04)
Shrewsbury Town ----- Gary Peters (Nov-04)
Bury ---------------- Chris Casper (Oct-05)
Bristol Rovers ------ Paul Trollope (Nov-05)
Mansfield Town ------ Peter Shirtliff (Nov-05)
Stockport County ---- Jim Gannon (Dec-05)
Chester City -------- Mark Wright (Feb-06)
Torquay United ------ Ian Atkins (Apr-06)
Peterborough United - Keith Alexander (May-06)
Swindon Town -------- Dennis Wise (May-06)
Walsall ------------- Richard Money (May-06)
Grimsby Town -------- Graham Rodger (Jun-06)
Hartlepool United --- Danny Wilson (Jun-06)
Lincoln City -------- Jon Schofield (Jun-06)
MK Dons ------------- Martin Allen (Jun-06)
Notts County -------- Steve Thompson (Jun-06)
Wycombe Wanderers --- Paul Lambert (Jul-06)
Note: Steve Evans of Boston was reappointed in March 2004. He had an earlier spell as manager at the club.