A fabulous DfE funded site aimed at enhancing professional development in Maths teachers across all sectors and levels. There are news items, message boards, regular email magazines, stacks of resources and links to some very interesting blogs from maths teachers, etc.
I was introduced to this site in 2008 whilst studying for the Level 5 Additional Diploma in Teaching Mathematics and would now be lost without it. Becoming a member of the NCETM is an absolute must for anyone undergoing professional development in teaching numeracy/mathematics. The forums are lively and enlightening – I recommend a visit to the Maths Cafe to get a taster.