pattern blocks

    (available in wood or plastic.

    Avoid the "foam" ones, because in my experience they are less accurately manufactured)

pentominoes (based on 1-inch squares.

    I recommend pentominoes that are not scored between the squares, but unfortunately, they seem to no longer be available.)

patty paper

tangrams

Geometry Labs template (template documentation: PDF)

CircleTrig Geoboards (much info on this on my Web site and in the Geometry Labs book)

If you are not interested in circle geoboard activities, 11 by 11 geoboards are easy to find with many publishers.

Polydron Frameworks Archimedean Solids (starter set, will make any Archimedean solid | class set, will make all of them at once)