As you keep on adding more and more machines to Puppet, it tends to get slower. A major reason for this is that Puppet uses Webrick by default which it ships with. While webrick is good for testing and small scale deployments, it performs poorly as the number of machines increases. So a good alternative is to use Apache or Nginx in combination with mod_passenger or Unicorn. I'll show you how to use Apache + mod_passenger in a very concise way. I think using other combinations should be equally easy.
Install httpd and mod_passenger into your puppetmaster box. Use Phusion Passenger RPM Repository for mod_passenger if it is not available for your distribution.
# yum install mod_passenger httpd
Now you got to configure passenger. Include the passenger module in apache config and set various params. To keep the configs clean, I recommend creating a separate file and putting passenger related things there. My passenger config looks like this.
Finally let us create a virtual host for the puppet master. Remember that not only apache has to serve catalogs but it also has to take care of SSL as well. So you need to point apache to the certs and the CA created by the puppet master. You might need to install mod_ssl for turning on the SSLEngine. You can check out my apache virtual host config here. RequestHeader(s) are used to set the certificate verification result as environment variable.
You can tweak around a bit, specially with passenger config to suit your infra needs. If at all anything is not clear please ask me in comments.