One of the frustrations I have with MobileMe at the moment is that if you want to go wireless (Push) to your iPhone or iPod touch, you can only push out your iCals to the device if they are the ones you've created and not ones that you've subscribed to.
You could still sync them via iTunes, but then you'd have to go back to syncing (via the USB cable) every time there was an update. I much prefer the wireless method.
So here's a workaround for now (especially for iCals that don't change that often):

1) Let's say you want your Birthday's iCal or your US Holiday's iCal on your iPhone. Select it in the source list.
2) Choose Export from the File Menu.
3) Choose a location to export it to such as your Desktop and click the Export button.
4) Now choose Import from the File menu and leave it on the iCal choice and click Import
5) Choose the iCal on your desktop that you exported in step 3.
6) It will prompt you to choose which calendar to add the new entries to? Be sure to choose "New Calendar" from the pop up menu.

Now you'll have a New local version of the iCal that you were subscribed to (basically a duplicate) that you can now sync wirelessly to MobileMe and then to your device. If Apple ever updates MobileMe to work with subscribed iCals you can simply delete this new iCal that you imported and go back to using the one that you're subscribed to.