Walking on the Amalfi Coast – an excellent, detailed guide to the best walks in the region. You can also download individual walks on the Cicerone website.
Walking In Sorrento & The Amalfi Coast – a great pocket guide to walks in the Amalfi region with maps and public transport info.
Officine Zephiro – guide books and maps for Sorrento, Amalfi, Capri & Cilento (very knowledgable local company based in Amalfi – all materials available in Italian or English)
The Map Shop – huge list of every type and scale of map for Italy (and one of the best online map shops worldwide).
OpenStreetMap – fantastic crowdsourced maps with several different map layers to view – zoom in to find numerous walking and cycle trails.
MapMyRun – my bible! It’s the only site I’ve found where you can look at a place and flick between Google Transport Maps, Google Satellite, World Topographical maps and OpenStreetMap data. It’s incredibly useful and I use it before every walk. Sign up and use the ‘Create Route’ tab to get to the map page.
GeoPortale (Campania) – technical map data and projects