UK QGIS
You can find out more about the UK QGIS group via our qgis.uk website.
We have a Google+ group setup, as well as a Mailing list on which users discuss all manner of QGIS queries or thoughts.
It’s early days yet but there is a Github page too.
QGIS in general
The QGIS project – find out more about project QGIS and how to download it and start mapping.
QGIS on facebook
QGIS forum on LinkedIn
GIS StackExchange – a great place to learn about QGIS by asking and viewing questions.
QGIS UK 