I am on iCal Version 5.0.3 (OS X 10.7.5)
I have been able to sort my calendars alphabetically by creating a new group (command + shift + N), dragging my calendars into that group, and then back out again. To "group" my calendars without having to use actual folders, I usually just add characters to the beginning of groups (e.g. aCalendarX, aCalendarZ, bCalendarY, bCalendarA, etc); not pretty, but it works.
If you are using the group function, it is quite handy b/c you can toggle entire groups on/off.
Hope that helps, or if you've already figured something out, hope this helps the next person who stumbles upon this topic.