Accessing computers on your own network and those that are remote is set to become a much easier affair in OS X 10.7 Lion with Back to my Mac seemingly set to become free and usable with an Apple ID.
From what can be deduced in the developer preview of Lion, it seems as though the previously MobileMe only service of Back to my Mac which allows users to access remotely another Mac for file or screen sharing, may be becoming free. The basis of this speculation is the inclusion of the option to access a networked or remote Mac, PC or other device by using an Apple ID, which unlike MobileMe is a free service from Apple. Unlike the Back to my Mac service however is that the Apple ID access prompt is also an option when you wish to access a Time Machine disk and even printers.
Apple has also added the ability to add an Apple ID directly to a user account, which can be found in the Users and Groups pane of the Settings application in Lion. Finally it seems as though OS X has improved its support for detecting Windows PCs on a local network, with them now automatically showing up in the Finder sidebar, just as Macs do in Snow Leopard and without the need to add their IP or Bonjour address!