SurveyMonkey
https://www.surveymonkey.com
Survey Monkey is an easy-to-use web tool that allows the user to create polls and surveys and collect data on whatever subject they choose.
I would find this useful in a classroom for two reasons; one would be to collect data from my students on what they prefer, how they learn best, etc. As well, students could create surveys and use the data for a lesson. For example, an elementary math lesson could be made by making the data they have recieved from SurveyMonkey into a graph.
By using SurveyMonkey, children would be able to see that the data they recieve is from their classmates and make it more 'real' for them. Students may not quite understand the process of collecting and gathering data until they are involved in the process themselves.
SurveyMonkey is an all-ages site and would be optimal for children above the grade 2 range.
