Here are some links to related sites that you may find interesting.
I have recently produced a photographic Guide to Harvestmen of the British Isles for the Field Studies Council. Many of the images from the guide can be seen on the Arachnids/Harvestmen tab of this website. In the FSC guide a key to species and introduction to the Opiliones accompanies the images. The guide is available online at, http://field-studies-council.org/publications/pubsinfo.aspx?Code=OP140 The Opiliones Recording Scheme, with more of my images, can be found at http://srs.britishspiders.org.uk/portal.php/p/A-Z+Species+Index/r/view/s/*.
A comprehensive source of Opilionological Taxonomic Literature can be found at ARACNOLAB: http://www.museunacional.ufrj.br/mndi/Aracnologia/pdfliteratura/pdfs%20opiliones.htm.
A good selection of German harvestmen can be seen at : http://www.spiderling.de/arages/index_eng.htm.
Another source of information on British Harvestmen is at: https://sites.google.com/site/opilionesuk/.