This is a great tool that I read about in Nik Peachey's blog, Nik's Quick Shout
It allows you to embed a video and create a quiz based on it. Once you are done, you can grab the code to embed in a blog, wiki, etc. As my students love working with video clips, I find this tool of enormous pedagogical value since students are developing vocabulary and listening skills through a highly motivating activity. This has also proved a valuable resourse to entice students to visit their wiki, where, alongside their working spaces, they now have a video page.
The only weak points I have encountered so far are that ESL caters solely for multiple choice questions. Besides, if you want to embed the code on Ning, you'll find that you can only do so on the pages that have a text box (Main, Members, Groups) Apparently, "iframes" can only be added to text boxes in Ning.