Answer Pad is one of the best free (per 1 teacher - 8 groups & 200 students) tools around for mobile devices. This is a easy to use graphical student response system that helps turns a classroom paperless by allowing for all testing/assessing to be done on mobile devices. Educators use the web interface to create lessons then push them out to student devices using the free TapIt app. This allows them to guide learning, differentiate instruction, and assess students in real-time.
Also, there are lots of templates for teachers to browse through and customize to meet their needs. For example, an educator can download a template of a graph, map, clock, grid etc. and then draw/type/annotate on it to use w/ their students.
Below is a brief demo...
I highly recommend checking out Answer Pad by clicking here!!!
*Answer Pad is an advertiser of Technology Tidbits.