When people find out I use MobileMe, their first question is always "How do you like it?" Well, actually, their first question is usually "You actually use MobileMe? Why?!" but it's always followed by asking how I like it. The answer is that I actually like it fairly well. It has its quirks and shortcomings, but as a simple solution that invisibly unifies my calendar, contacts, mail, and photo albums across my phone, laptop, and the web, it's pretty hard to beat. It is far from perfect or complete, but the highest compliment I can pay to MobileMe is that I seldom have to think about it at all.
With MobileMe's impending demise at the hands of iCloud, now may be a good time to do some housekeeping and clean up any unneeded MobileMe clutter. One good place to start is with your calendars — not events and appointments, but your actual calendars.
One of the convenient features of iCal (and, therefore, MobileMe) is the ability to subscribe to pre-built event calendars. In fact, Apple has long maintained a directory of such calendars: apple.com/downloads/macosx/calendars/
One WebCal calendar that I subscribed to was one to remind me once a month to completely discharge my phone battery, per Apple's recommendation (apple.com/batteries/). After a few months, I decided that I was running my batteries down often enough without needing a reminder, so I unsubscribed from the calendar. That removed it from iCal on my laptop and my web calendar on MobileMe, but not from my phone. What's more, I soon discovered that there's not a way to delete a calendar directly from an iOS device (at least up through iOS 4.2).
After some research, it appeared that my problem was because I had initially subscribed to that calendar from my phone, then synced it to MobileMe and iCal, rather than the other way around. After such a long period of time, though, I couldn't recall exactly how I'd subscribed, which certainly hampered my effort to find a solution.
I finally found a solution that worked for me on Apple's forums, so I present it here in the hopes that it may help others who find themselves in the same fix I was in.
This is a frustratingly round-about way to solve what should be a simple issue, but it's what worked for me and others in the Apple forums. Although I haven't tested the process personally, there are some users reporting that it will also work to solve similar problems in Mail and Contacts.
Hopefully iCloud will address some of these problems, as it will replace these features from MobileMe. But before making the transition it's a good time to check and make sure you have removed, resynced, and reset anything that might still require an active MobileMe account to clean up.