I had to set up a customer's Rails application to run using SSL+HTTPS this morning. Based on a few positive web blog articles I decided to try Igor Sysoev's nginx web server. If you first build and install OpenSSL and the Perl regular expression library, then build nginx with
you should be all set to use HTTPS. Clustering mongrel is also simple; I used this nginx.conf file from Brainspl.at as an example and I was set up and running very quickly. Good stuff!