Fauxflash is a free flashcard service. You'll be able to create as many decks as you want, and to access the ones that others have created without having to pay a thing. All you must do is to sign up for the service.
It appears that this company is in the process of creating an app for Android and iPhone/iPad
This Diigo group was created for a Summer Academy professional development class that was taught in 2011. This class is to give teachers the time to dive into online tools they may never have been able to explore in the past. They will be adding their online "finds" to this group and I thought you might enjoy seeing what they add!
Why use Twitter and how does it work in a class? This article goes on to discuss using Twitter with an online classroom, but many of the basic pros/cons would work in any classroom.
Social Networks that are supposed to be safer for younger kids. This article is from Common Sense Media and gives parents and teachers other options for teaching social networking in a safer environment.
Here is an example of a website a teacher is using for reading "The Devil's Arithmetic". I have saved it as a skeleton for planning student websites. If you use Google sites, you can also include student discussion boards, shared Google Docs, etc.