CoolMath – an old, familiar math website has recently launnched a set of virtual manipulatives including a nice interface for base-ten blocks. Becuase they are just rolling this content out now, the number of manipulatives is limited to the base ten blocks, a numberline, patterrn blocks and ten frames.  However, CoolMath has been a resource for teachers for many years now, and we can likely expect the virtual manipulative resources to continue to grow!