Thawte SSL Certificate

Thawte offers several different SSL Certificates to to secure your website with.  Their offering includes EV certs, wildcard certs for subdomains, and 128 and 256 bit encryption.  There certs have over 99% browser compatibility.  Here is a breakdown of their annual pricing if you purchase for 2 years.

SSL123 $259
SSL Web Server $449
SSL Web Server with EV $995
SGC SuperCerts $1199
Wildcard SSL Pricing Varies