Forget MobileMe the cheapest way to keep your home, work and iphone calendars (& contacts) in sync is by using Google Calendar and a program called GsyncIt*.

I've installed GsyncIt on my work and home PC, and both of these sync my Outlook to an online Google Calendar account. My iPhone also syncs to my Google Calendar account using (on an hourly basis) the new CalDav protocol released with the iPhone 3.0 OS.

Its pretty straightforward to set up, but requires a bit of thought to avoid calendar entries being duplicated/erased. I guess Mobileme is easier to set up, but at $99 a year its a real rip off.

* Google have a freeware program called Google Calendar Sync, but it is extrememly buggy and will fail to sync a great number of calendar entries (e.g. meetings not arranged by you) hence why GsyncIt is the best choice for the job.