>>"Is there any way to get push mail working on SBS2008 without having to get an SSL certificate?"
Yes you can use a self signed certificate generated by the SBS when you run the "configure my internet address wizard". This certificate needs to be installed on mobile devices or remote clients wanting to use services such as OWA and RWW. A purchase certificate does not have to be installed on mobile devices or clients as it is automatically accepted.
>>"Is there any way to get an SSL certificate issued while on a dynamic IP address?"
Yes. You need to use a DDNS service such as dyndns.com or no-ip.com and so that you can use your domain name you need to purchase their "custom DNS service" (dyndns) or "plus managed DNS service" (no-ip) for about $30 /year
