I moved to Wiggio after Ning went to a fee-based site. As a teacher and a coach I could have gotten a free Ning site, but it was only the basics. I love the flexibility Wiggio gives me to upload video and audio. I will use it again next year and am promoting Wiggio to everyone I meet.
it provides everything you need to work productively in your groups, without bogging you down with complexities and unnecessary features. Wiggio is currently used by over 100,000 groups
The other important aspect is to keep the number of windows that have to open to a minimum. If too many windows or links to resources are spread throughout the site, students get confused and frustrated quite easily.