Zamzar - convert document, eBook, image, audio and video - free online file conversion. Diigo. Wiffiti. Wiffiti is coming soon to education and I believe that it will make a big splash in classrooms where phones are allowed to be a part of the learning experience.
Teachers want the ability to get immediate feedback from students. We have come up with several ways for this to occur (response clickers, web based polling, real time collaborative documents) but we have yet to discover a way to incorporate text messaging...until now. The first site which allows students to text in comments is here with Wiffiti. Currently their site says that they will be undergoing a major overhaul in the upcoming weeks.
You can request an invite to their beta testing and until then try it out with what is currently on the site. 7 Services for Sending Group Texts to Parents and Students.