Here are some web links of interest to researchers and students in mathematics education.
Sir William's Review of Mathematics Teaching in Primary School and Early Settings - the final report is now available.
International Newsletter of Teaching and Learning Mathematical Proof is a very good reference site for new development/publications on proof and proof production in school as well in university mathematics.
Here is a very comprehensive list of the main journals in mathematics education - with weblinks.
Here is a website dedicated to history of mathematics based at the School of Mathematics and Statistics, University of St Andrews, Scotland.
The Notices of the American Mathematical Society is a monthly publication for mathematicians and people interessed in mathematics. it often publishes articles on mathematics education. It is free to read on their website.
The Philosophy of Mathematics Education Journal is hosted in Paul Ernest's website, and it is also free to download.