Weekly teasers are added at each grade level, with solutions posted one week later. The site contains an archive of past brain teaser's for each level. This is another site offered by the Swarthmore Math Forum . Specific questions can be submitted to the site.
Students can submit projects to be included at the site.
There is a list of suggestions for various topics as well as a sampling of student projects. These math problems are offered by the University of Idaho Math Department for students up to grade 12, and may be solved individually or in small groups. Interesting problems to solve presented by the Swarthmore Education Department's Math Forum . You need to register to have an id and password, but access is free. The MathDEN has four levels of problem sets, and will keep track of your progress.