I believe some of the best partner sites for Yedda would consist of sites with communities, which could contribute the largest number of contributors or knowledge to the knowledge base.
For example, Blogging sites such as:
Blogger
Wordpress
Where as the Yedda Widget is a default module in their blog templates. That way, when new users and existing users set up their blog accounts they automatically or have a emphasized option to add the Yedda 'ask a question' widget to their blog.
This would greatly increase the amount of questions as well as the amount of possible answers that are feeding into the Yedda community from various blogs, locals, and domains on a variety of subjects and expertise.
In addition, I believe established social networking communities such as Myspace, Facebook, and any other profile-driven communities where the widget could be added easily or by default would be valuable in the goal of expanding the community and knowledge base of Yedda.