In July 2005, I attended the 5th Institute of Mathematics Pedagogy (IMP '05) held at Sheffield University. This was led by:
John Mason
Anne Watson
Malcolm Swan
Open University
Oxford University
University of Nottingham
One of the most practical and useful ideas I picked up at this event (it was more like a retreat than a conference) was an inspiring suite of assessment tasks that Malcolm Swan has been trialing as an alternative to pencil and paper testing regimes.

I have found that teachers and students alike are engaged when having to complete a sorting task, with peer coaching arising without any intervention. As a teacher, it is very easy to see if groups of learners are 'stuck,' and need some in-the-moment micro-teaching to resolve a misconception.

Malcolm Swan has written a really useful book, available in PDF format.