Ssl – Using wildcard SSL certs (chain certificate) with mod_gnutls

The main limitation is that with one ip address you can have one ssl certificate.

Since you only want ssl on the blog then there's no problem with the setup you've proposed, just make it the only virtualhost listening on 443

# Virtualhosts on ports 80 and 443
NameVirtualHost *:80
NameVirtualHost *:443

# rewrite blog traffic to https
<VirtualHost *:80>
        ServerName blog.example.com
        DocumentRoot /var/www/blog
        RewriteEngine On 
        RewriteRule ^(.*)$ https://blog.example.com/$1 [R,L]
</VirtualHost>

<VirtualHost *:443>
        SSLEngine on
        SSLCertificateFile /etc/apache2/ssl/server.crt
        SSLCertificateKeyFile /etc/apache2/ssl/server.key    
        ServerName blog.example.com
        DocumentRoot /var/www/blog
</VirtualHost>

<VirtualHost *:80>
        ServerName othersite.example.com
        DocumentRoot /var/www/other/
</VirtualHost>

The slight limitation here, is that the blog will catch all https traffic here, regardless of hostname, so https://othersite.example.com will point to the blog, and generate errors because the name doesn't match the certificate, but there's no way around that with one ip address.

The private key is mydomain.key which you generated along with the CSR.

What GoDaddy has sent you is the public key (the certificate file mydomain.com.crt, as signed by GoDaddy), as well as the intermediate certificate chain for GoDaddy that complete the chain of trust between your certificate and what an end-user's browser knows about (the gd_bundle.crt file).

I'm not specifically familiar with ELB, but looking at this documentation page:

http://docs.amazonwebservices.com/ElasticLoadBalancing/latest/DeveloperGuide/US_UpdatingLoadBalancerSSL.html

You will supply your mydomain.key file for the private key, the mydomain.com.crt file for the public key, and the gd_bundle.crt file for the certificate chain.