It's actually pretty easy, but odds are good you'd never find it on your own. Open Outlook to the Calendar view and find your calendar folder in the navigation pane on the left side of the window -- it will simply be called Calendar.
There might be other calendars listed as well, especially if you have shared team calendars using SharePoint. Don't worry about those.
Right click Calendar and choose Properties. Then click the Permissions tab.
Now just change the Read permission from Free/Busy time to the entry that includes subject and location, or choose Full Details. Then click OK.
From now on, everyone will be able to see your appointments rather than knowing your time is blocked out. If you set up an appointment you genuinely want to keep private, be sure to click the Private button when you create the meeting.
Of course, this trick only works if you use Outlook on Microsoft Exchange Server, but you knew that already, since you can't share Outlook's appointment details with people over the Internet.