If you use GoDaddy your sites may not work because GoDaddy is too cheap to provision enough servers to handle the load. So don't use GoDaddy.
Namecheap SSL cert (RapidSSL): $10
StartCom SSL cert: $0
Gandi.net SSL cert: $0 with domain registration
I am a happy Gandi.net customer but I had never heard of this! Looking back it's mentioned in the renewal confirmation email "Did you know? Since February 20th 2009, when you create a domain name at Gandi, you also benefit from a standard Gandi SSL certificate for one year!" but of course I didn't pay much attention to those.
The fine print for the SSL certificate is "Included for free the first year with the purchase, transfer, or renewal of your domain name. €12 euros excl. vat per year for its renewal. Offer valid until December 31st, 2011."