I've never understood the word 'testimonials' within a project. I think everybody knows about writing reviews.
OpenNTF hosts an IdeaJam from 07/14/10 until 07/16/10 to identify the most important web site improvements and new services. To create your own idea just click 'Post my idea' and choose the ideaspace 'July2010' as well as the tag 'July2010'. To vote and comment on ideas select the ideaspace 'July2010' and then open one of the views 'Recent', 'Popular' or 'Recent Comments'.
In order to add ideas, votes or comments you need to login with your OpenNTF credentials. If you haven't registered you can do so here.