Comodo now offers Unified Communications Certificates to use with your Exchange 2010 Server or Office Communications Server 2007
Traditional SSL certificates provide security for a single fully-qualified domain name. Wildcard certificates can cover all first-level subdomains of a domain. UC Certificate, also known as SAN Certificate, with Subject Alternate Names (SAN) allows hosting multiple SSL-enabled websites on a single server eliminating the need for binding different IP addresses to different SSL certificates. A single Unified Communications Certificate / SAN Certificate can cover many different domains - that's less than $300 for a single certificate covering up to 3 domains (PRICE per domain per year thereafter).
* Free 1 year PCI and website scanning offers are limited to one license per-account.