Currently Being ModeratedJun 19, 2013 3:33 AM (in response to seymours)
You need to have an iCloud account and locate your calendar on iCloud (rather than 'On My Mac'). Then you can share it publicly so that anyone with iCal or another CalDAV client can subscribe to it (read-only) - details here:
The alternative is that you would have to be running a CalDAV server and publish to that, which is probably more hassle than you would care to contemplate.
Currently Being ModeratedJun 19, 2013 8:31 AM (in response to seymours)
If you share it publicly from iCloud anyone can see it in iCal or other suitable clients, but they can't edit it - I would imagine you wouldn't want them editing it, but if you share it privately they can but they have to have iCloud accounts to access it.