Links

Cambridgeincolour Lots of tutorials and technical articles abouts digital sensors, diffraction, sharpness etc

DOF calculator I From Enrico Savazzi website, based on Lefkowitz formula 

DOF calculator II From nikon's microscopy site. Very useful to find the number of shots needed in a stack

Macrosmuymacros    Thread in Canonistas.com started by Javier Replinger which after more than 90 pages and 170.000 visits made us make this site (in Spanish)

Makrofokus.se Macro web site managed by John Hallmen and Stanislav Snäll with very good articles (in Swedish)

Photomacrography.net best source of information for macro and microphotography

The macrolens collection database  The most complete database of macrolenses online, by Dr. Klaus D.  Schmitt

 Photographers

John Hallmen     John Hallmen's flickr site 

Morfa.se            John Hallmen's website 

Javier Replinger Javier Replinger's flickr site

Nikola Rahmé    Nikola Rahmé's flickr site

Javier Torrent    Javier Torrent's flickr site

Software

Combine ZP       Free focus stacking software

Helicon Focus    Another focus stacking solution 

Zerene Stacker  Focus stacking software developed by Rik Littlefield; one of Photomacrography.net moderators

Hardware

Stackshot Electronically controlled macro-rail

Arduino  Open source hardware/software platform for DIY projects

More to come