We are having our web application distributed across a number of subdomains on our hosting account. We want a single SSL certificate solution for our web application?

You can use RapidSSL Wildcard and you buy its Certificates from here . Here. .it can be used for all your subdomains

A special type of SSL certificate known as a 'Wildcard' certificate caters specifically for services distributed across a number of sub domains. RapidSSL wildcard and Business ID wildcard from Geotrust at an economical price with great pricing options are good solutions to your wildcard certificate needs.