Ubuntu Feisty has a bug where the command apache2-ssl-certificate is missing. This is a well documented bug. Here is the file you need to download to overcome this defect to create a self signed certificate. After you download, follow the notes below to copy the downloaded files to the location where they are supposed to be present.

1. Extract the package
2. put ssleay.cnf to /usr/share/apache2/
3. put apache2-ssl-certificate to /usr/sbin.
4. Create /etc/apache2/ssl directory.

Now apache2-ssl-certificate script should work. Please follow this link if you want to know how to use it.