This page is a big bucket of links that I have found useful or enjoyed during the course of my research. Please let me know if you have any suggestions or recommendations for me.

Organisations
International Association of Hydrogeologists
New Zealand Hydrological Society

Studying geoscience at Tübingen
Integrated hydrosystem modelling PhD program
Applied & environmental geoscience MSc program

Blogs that I like
GeoSphere - An EGU network blog covering many bases
Walking Randomly - Excellent and amusing writing about scientific computing
planetwater - The blog of Claus Haslauer (my supervisor)

Some fundamentals
SEPMStrata - Everything you ever wanted to know about sedimentary geology but in a way that everyone can understand
Paul's math notes - This website got me through the first semester of my MSc. Excellent theory and exercises in fundamental mathematics
edX - A good source of open courseware, or MOOCs if you prefer
BitBucket -  a good place to stash your codes
Purdue Online Writing Lab - This website will make you a better (at writing) person