John & Anne Nuttall's website - a must for summit baggers
Alan Dawson's website - for up-to-date information about the Marilyns
Statistical Topics in Hillwalking - home of the Database of British and Irish Hills (DoBIH)
G and J Surveys - YouTube channel by John Barnard, Graham Jackson and Myrddyn Phillips, hosting clips about some of their past, present and future surveying projects
Myrddyn Phillips interviews - Myrddyn Phillips's YouTube interviews on hill bagging and related topics, including interviews with Graham Jackson from the DoBIH survey team, and John and Anne Nuttall
Summit Photo website - Collection of hill summit photographs, which can be viewed via thumbnail links from the mountain details pages on this website. If you would like to contribute photos to the collection, please click on the link
Ordnance Survey - Britain's national mapping agency
Streetmap - excellent source of maps in digitised format - I obtained most of my background maps for this site from here
Bing Maps - another source of digitised maps
GPS Utility - GPS Software to download - even the free unregistered version is good
Garmin - GPS equipment manufacturers
TACit Tables - source of definitive lists of hills in Britain
Scottish Mountaineering Club (SMC) - publisher of Munro's Tables and other Scottish hill guidebooks
Phil Newby's GPS site - waypoints in all sorts of formats, as well as lots of other GPS stuff
UK Rec Walking Discussion Group - lively online discussion on walking related topics
RHB Discussion Group - for Marilyn bagging and other hill-walking related topics
UK Walking Forum - Walking and Hiking Forum
Mad about Mountains - Mountain info and photos, and descriptions of walks to Marilyn tops
Been There - Done That - An "unofficial guide to Great Britain"
Where's the Path - walking diary of some fellow Marilyn and County Top baggers
Lakeland Walker - walking diary of a Wainwright bagger
Lonewalker's Walking Diary - "the thoughts and musings of a fat fellwalker"
Welsh 3000s Challenge / 14 Peaks / 15 Peaks
Wilderness Wales - lots of photos and other info on Welsh mountains
The Pennine Way Site - good source for Pennine Way info
My Pennines - walking diary, info and routes of a Pennine walker
Peak Bagging - The English Nuttalls - walking blog and routes of a Nuttall bagger
Simon's Mountain Lists - hill list history, photographs, and discussion on hill-bagging
Summit Journeys - Mountain walking and rock climbing holidays and courses
Mountain Views - Hillwalking Resource for Ireland, with similar aims and features to this site
UK Prominent Peaks - Prominence based hillwalking challenges
The Happy Hiker - walking routes and advice, with GPS route downloads
The Wasdale Web - Online guide to Lakeland's finest valley and surrounding area
The Mountains of England and Wales volumes 1 & 2 by John & Anne Nuttall - Cicerone Press, 1989 & 1990 - ISBN 1 85284 036 6 & 1 85284 037 4
The Relative Hills of Britain by Alan Dawson - Cicerone Press, 1992 - ISBN 1 85284 068 4
A Pictorial Guide to the Lakeland Fells books 1-7 by A Wainwright - Westmorland Gazette & Michael Joseph Ltd, 1955-1966
Mountain Tables by Michael Dewey - Constable & Co Ltd, 1995 - ISBN 0 09 474520 X
Complete Lakeland Fells by Bill Birkett - Harper Collins Willow, 1998 - ISBN 0583322093
The Mountain Summits of England and Wales by Chris Buxton & Gwyn Lewis - Red Dial Publications, 1986 - ISBN 0 9511723 0 1
The Mountains of England and Wales by George Bridge - Gaston's Alpine Books & West Col Productions, 1973 - now out of print