I don't know if possible but here's something to think about (keeping in mind a single install with multiple child sites & using SSL).
What if a generic SSL cert is placed on the IIS web for mojoPortal and it has a generic domain name such as securedomain.com. Would it be possible someday to allow sites to share that domain just for certain pages? Say the user has a donation page and they don't care if the URL changes to securedomain.com just for that page. Ideally of course the skin would still brand that page and it would flow like the other pages in their site, but just for those secure pages they share a domain name and SSL cert.
I do this now in a manual sort of way using IIS, virtual directories and a shared SSL/Domain name. Example:
https://www.secure-ssl-web.com/1020/getinvolved/donations/default.asp
I can fully appreciate how complex and impossible this might be, but I just wanted to throw it out there in case anyone with more knowledge than me has a good idea. It sure would be a HUGE benefit to have just one install and multiple sites being able to use SSL to some degree (while not requiring a SSL cert for each site). I'd use iFrames if it wasn't for the URL and little lock problem. While secure, users wouldn't visible know it unless they view the frame properties.
Joe mentioned in another post that you could have just two installs, one for SSL sites and one for non-SSL. That's a pretty good second best bet. My main concern there is that with my luck a month later one of those non-ssl site will want to add a SSL application and then I'm in trouble, LOL.
Thanks everyone, mojoPortal is simply amazing!!!!!