It can be difficult getting good photographs of echidnas, mainly because they are so low to the ground and often vegetation obscures the view.
These photos are the best of many I've taken, and as I've become very fond of these guys they now have their own dedicated page.
They really are interesting animals, to learn more, you can try these links:

http://www.echidna.edu.au/monotremes/echidna_research.html
https://www.parks.tas.gov.au/?base=4796
And here's a scanned copy of a fact sheet from an Echidna CSI presentation we attended. Thanks to Peggy Rismiller at the Pelican Lagoon Research Centre on Kangaroo Island.

Many of the photos are from our time in Tasmania, these echidnas are :
Tachyglossus aculeatus setosus,
also, from our property at Prospect Hill in South Australia, another subspecies,
Tachyglossus aculeatus aculeatus