Glossary (as far as I can glean!)
Dysse: 'dolmen' = burial chamber, often with a mound (plural – dysser)
Dyssekammer: 'dolmen chamber' = burial chamber – as we usually use dolmen
Runddysse: 'round dolmen' = a chambered round barrow (plural – runddysser)
Langdysse: 'long dolmen' = a chambered long barrow (plural – langdysser)
Jættestue: 'giant's stones' = passage grave (plural – jættestuen)
Høj: 'hill' = barrow
Skibssætning: 'stone ship' = megalithic boat-shaped setting
Books & maps
For our trip Jane and I used Julian's The Megalithic European (see link at top of page to 'The Books') and James Dyer's Discovering Archaeology in Denmark (1972, Shire ISBN 0 85263158 8).
For Langeland, we also used the Danish language Oldtidsmindser På Langeland (1996 Langelands Museum ISBN 87 88509-133) available at the Tourist Information office (and, I would imagine, Langelands Museum itself) in Rudkøbing, Langelands. It doesn't seem to be available on their website though – langelandsmuseum.dk/museum_en
We also got a useful 1:50,000 map/leaflet in English Six cycling trips on Langeland (ISBN 87-7343-380-2) from the Tourist Information office.
Mapwise, we used the Euromap 1:30,000 of Denmark (ISBN 3-575-03112-6), which allied to some maps printed from the Visit Denmark website (see below) allowed us to find pretty much everywhere we looked for.
I also did some web research with limited success. I have posted the most useful site I found for the whole country (Visit Denmark) in the Links section below. I've posted a link specifically for Northern Jutland on the Jutland page. There is also a great PDF document available for some of the sites on Als, see Links on the Als page.