On Friday, Microsoft opened the previous private online Beta of Popfly to the public.
Using Microsoft's Silverlight technology, Popfly can interface with Flickr, Facebook and more and offers webpage on-line development, mash-ups (with an easy-to-use interface) and more.
There are some caveats in the FAQ's but Microsoft does make mention of Firefox compatibility. We had no difficulties creating a quick Flickr mashup using Firefox.
We found it a little buggy at first, but then outright fun once the components loaded to our test box. The webpage designer is similar to Office Live but smoother with much better WYSIWYG editing.
User will have to have MS Silverlight installed to try it.