British Beekeepers’ Association: http://www.bbka.org.uk/
Kent Bee-keepers’ Association: http://www.kentbee.com/
BeeBase, the National Bee Unit: https://secure.fera.defra.gov.uk/beebase/index.cfm
The Co-operative’s Plan Bee campaign: http://www.co-operative.coop/Plan-Bee/
The ‘Hive Talking’ site supported by Plan Bee: http://www.urbanbees.co.uk/maps/
and our own group on Facebook at https://www.facebook.com/groups/359167444256663
For anyone interested in other social insects and solitary bees, there’s an interesting site here in the US (thanks to Amy and Shelley for the info), plus the BWARS site in the UK, and the BBCT site for anyone looking to learn about bumbles. For a general international review, the IBRA site is very good.