Office.com calendar publishing ended on April 4, 2014 You are no longer be able to share calendars by publishing to Office.com. You'll need to have your own WebDAV server to use for publishing and sharing calendars.
A hotfix is available for Outlook 2010 that adds a warning to the Calendar publishing feature, alerting the user that as of April 4, 2014, Office.com will no longer host published calendars. Get the hotfix at Description of the Outlook 2010 hotfix package (Outlook-x-none.msp; Outlookintl-[Language-Code].msp): October 8, 2013 This hotfix will be included in a future update.
If you receive this error:
Task 'Published Calendars' reported error (0x8004010F) : 'The operation failed. An object cannot be found."
You can remove the calendar in File, Account Settings, Published Calendars or by using the /cleansharing switch.
To use the /cleansharing switch, close Outlook. Press Windows key + R to open the Run command, then type or paste the following in the Run field and press Enter.
outlook /cleansharing
The /cleansharing switch removes all RSS, Internet Calendar, and SharePoint subscriptions from Account Settings, but leaves all the previously downloaded content on your computer. This is used when you cannot delete one of these subscriptions within Outlook 2010 or Outlook 2013.
More Information
The content previously on this page was removed as it is now obsolete.
I seem to still be able to publish my free/busy information for people outside my organization to view via Outlook.com (not Office.com), which seems to work fairly well. Perhaps this only applies If you are using Outlook with an Office 365 (or Exchange) account?
For those that might not realize there may be additional options, it could be good to add a note that clarifies what external calendar publishing Microsoft does still support.
This page is specifically about the old Office.com service that was introduced with Outlook 2007 and discontinued. With this service, you could publish a calendar in a pst file and share a link to it - the recipients needed to open the link in a calendar program or subscribe to it in Hotmail or Gmail.
Exchange and Outlook.com accounts can share calendars with others (using methods specific to each account type) but pop3/pst users need to use a calendar service or WebDAV server to publish their calendar.
You can use icalx.com or keepandshare.com to publish from outlook. icalx only seems to display free/busy details, though.