I talked about Convergence before:
The main list of Convergence notaries is on this Wiki page:
I suggest to add every notary on that list and immediately disable it in the Firefox add-on options, then take your time to understand who is running the notary, why is running it, and if you think it can be trusted enable the notary, otherwise remove it.
If you want to run a notary, don’t forget to add it on that list afterward.
[Edit: changed list URL]