Note: this is really a how-to, w/o any in-depth explanation, just a note to myself.
Today, I needed to add SSL support to UMapper.com application running on my Slackware localhost. We use CA-signed certificates on our server, but for local box self-signed was quite enough (all I need is to be able to view development version of site via https). Here what I did:
1. Create private key:
$ openssl genrsa -out localhost.key 1024
2. Generate CSR (Certificate Signing Request):
$ openssl req -new -key localhost.key -out localhost.csr
3. Generate certificate:
$ openssl x509 -req -days 365 -in localhost.csr \
-signkey localhost.key -out localhost.crt
4. Make sure SSL is enabled in httpd.conf:
# Following two should be uncommented LoadModule ssl_module lib/httpd/modules/mod_ssl.so Include /etc/httpd/extra/httpd-ssl.conf
5. Edit httpd-ssl.conf so that virtual host users your created certificate:
# locate and edit cert.details. Make sure localhost.crt and localhost.key # are present (you either created them there or copied) SSLCertificateFile "/etc/httpd/certs/localhost.crt" SSLCertificateKeyFile "/etc/httpd/certs/localhost.key"
6. Restart apache:
$ apachectl restart
That’s it. Please note that browser would still generate exception (and it is a good thing, as otherwise certificates wouldn’t be that useful). All you need is to add your localhost as exception – since we really trust that details we provided during certificate creation are our own 
P.S. If you are getting “[warn] _default_ VirtualHost overlap on port 443,
the first has precedence”, add NameVirtualHost *:443 into your httpd.conf
