The webcal:// URL has become the standard URL used for subscribing to iCalendars on the web (see this site for an example). You can copy and paste the webcal:// URL into your iCalendar software to subscribe to the iCalendar.

You can also register webcal:// as a protocol in your browser’s settings and choose your iCalendar software as the helper application. Once you’ve done this, you can click the webcal:// links and they will be sent to your iCalendar software automatically.