For great walking information:

Ramblers
Ramblers, the national organisation of which we are a part

Derbyshire Dales Health Walks
For information on shorter walks to build up fitness

Peak District Boundary Walk
A signed walk following the boundary of the Peak District National Park

GeoWalk
A 135 miles walking route, with emphasis on the geology of the Peak District

Local organisations:

Peak & Northern Footpaths Society
Established in 1894, an organisation which looks after footpaths in the Peak District area

Derwent Valley Mills
Derbyshire's own World Heritage Site

Derbyshire Wildlife Trust
An organisation safeguarding our local wildlife and habitats

Cromford Canal
A group dedicated to restoring the Cromford Canal

National organisations:

Long Distance Walkers Association
For information on long distance paths in the UK

British Mountaineering Council
Primarily for climbers, but also relevant to walkers and ramblers

Ordnance Survey
Maps and mapping app, excellent for not getting lost

King Charles III England Coast Path
2700 miles when fully open but plenty to walk already

Wales Coast Path
An excellent guide to 870 miles of glorious coast path