Why don’t events created in iCal show up in my iCloud calendar?
It turns out I had to:


Add my iCloud account to iCal, in iCal > Preferences > Accounts.
Set my default calendar to one of my iCloud calendars, in iCal > Preferences > General.


See e.g.


http://www.mac-forums.com/forums/os-x-operating-system/253324-lion-ical-not-syncing-icloud-calendar.html
http://forums.macrumors.com/showthread.php?t=1249011


It seems a bit strange that I had to do this manually — you’d think just turning on Calendar syncing in the iCloud preference pane would do it.