There is a free trial version of the materials in the National Library of virtual manipulatives. Math topics Numbers and Operations, Algebra, Geometry, Measurement and Data Analysis & Probablity are covered. I did not come across anything asking for money so I a not certain there is a cost. There are tons of manipulatives to access from each of the above categories. This site is associated with the Uta State University.
Flickr allows students to take pictures and send them to a private space online. For example: A homework assignment for 4th grade mathematics students requires students to take pictures of different polygons they see in their everyday lives and instantly send them (along with a short text message describing the type of polygon) to a private space online. The next day in class the teacher can open the private space and use it to illustrate polygons and their connection to students' lives, leading to a lesson on how to measure these polygons. Both flickr.com and photobucket.com are sites that would allow this type of sharing. Both have a private mobile address that can be used on any mobile phone; the teacher just needs to set up the mobile account and give the students the address.
XP Math is a good place to find math games, math videos, math worksheets, and math e-books. The games section of XP Math offers games for basic arithmetic, algebra, geometry, and probability. Create an account on XP Math and you can keep track of your scores.