A mathematics teacher can always use more problems. Currently, NCTM is offering a free web site that offers a plethera of challenging problems appropriate for students in the grade 6-14 grade bands.
This resource actually is intended as a resource for students/teachers preparing for the 2005-2006 MATHCOUNTS competition, but is open to any teacher willing to register.
Each month, new problems are added to the site, all taken from past NCTM publications: Student Math Notes, "Menu" problems from Mathematics Teaching in the Middle School, and "Calendar" problems from the Mathematics Teacher.
Again, the problems are great....and the resource is free once you register...but why is it that when one registers, it is necessary to give a mailing address in addition to a e-mail address. I think someone is fishing for potential new members!