After some digging, Subject Alternative Names (SANs) is the way to have one certificate which holds many domain names in the SubjectAltNames field.
Here is a script to generate a CSR that holds different SANs: http://svn.cacert.org/CAcert/Software/CSRGenerator/csr
For more information: http://wiki.cacert.org/CSRGenerator
You can then have a certificate signed by CaCert for free, or any other vendor, like Comodo (UC Certificate).
If you want free cert, join the CaCert community> login to your acct> Add Domains that you own to the authorized list> Under server certificates click New and place your CSR> Submit and get your certificate.
Unfortunately there is no "paid" UC certificate free trial to test it in real world.
If you have more comments/thoughts on that, let us know. Shadi