I have a MobileMe subscription and a Mac at home with "Back to My Mac" enabled. When I'm away from home, this service lets me use another Mac to connect to my Mac back home and access file sharing, screen sharing, etc.
As far as I know, the service doesn't use any proprietary protocols, so in theory I should also be able to get "Back to My Mac" from a Windows PC. This MacWorld article explains how it works. Basically, it uses Wide-Area Bonjour to give your Mac a domain name like hostname.username.members.mac.com. Remote computers can find your Mac using that address, then connect to it using a private VPN. The "Wide Area Bonjour" part seems to make it a little more complicated than simply a regular domain name, though.
Note that I'm not interested in using the methods described by LifeHacker, which doesn't use the MobileMe service at all. I don't want to use a totally different dynamic DNS service. I'd like to use the one I'm already paying for, or at least find out why that's not possible from Windows.
Also, my primary problem is finding a network route back to my mac... once I've got that I know how to enable services so that Windows can talk to it.
UPDATE: Based on some additional research, it appears that Apple is only assigning IPv6 addresses to the hostname.username.members.mac.com names. So any solution will require enabling IPv6 support on Windows, if possible.