I recently needed to do some testing and needed to have a valid public SSL certificate and since it was only for testing, I preferred if there was no cost for this.
I came across StartCom – https://www.startssl.com/ – who offer FREE Class 1 SSL certificates.
These free certificates are Class 1 – meaning that there is minimal validation is done when they are requested and issued – however this is fine for testing but not really recommended for commercial use. From my testing, it appears that the issuing CA was automatically trusted by Internet Explorer and Chrome. These certs are perfect for testing over SSL.
For more info see the StartCom website – https://www.startssl.com/?app=40