Forrex:
http://www.forrex.org/
Sign up for the listserve. A really valuable service for keeping up with the latest news in forest hydrology - there is often a lot of content about monitoring.,

Stu Hamilton's Blog:
http://www.aquaticinformatics.com/blog/
Has topical commentary on issues related to water quantity

Catchment Conversations:
http://www.catchmentchange.net/category/catchment-conversations
Keith Beven is a leading thinker in the relation between data and science in hydrology.