July 19, 2010, 8:46 PM — OS X 10.5 and 10.6 both have the robust Screen Sharing program built in. It lets you access other 10.5 and 10.6 systems, and it's backward-compatible with the industry-standard VNC (virtual network computing) protocol. Unfortunately, on its own, that program alone isn't very good at reaching out over the Internet; it's best for connecting to computers that are hooked up to the same router, using Bonjour.
Paired with Back to My Mac, though, Screen Sharing becomes much more powerful--as long as the machines you want to connect with are all under you or your family's personal control. That's because Back to My Mac requires a MobileMe account, and each computer you want to use must be logged into the same account.
In addition to being built into OS X, Screen Sharing also has the advantage of managing multiple monitors really well. It's also relatively speedy and simple to set up. If you enable File Sharing on the remote system, you can transfer files over the same connection.
The biggest disadvantage of OS X's built in tools are that they require a MobileMe subscription. Back to My Mac can also be picky about the routers it will work with. Also, unlike some other remote-access options, they don't allow you to select a lower color bit-depth for the remote screen (which requires less bandwidth); you can, however, enable lossy compression, which can reduce both the bandwidth required and the quality of the screen image.
Assuming you have such an account, you enable Back to My Mac in the MobileMe preference pane. On that pane's Back to My Mac tab, you click Start to activate the service; a green dot appears when it has successfully registered your computer with the MobileMe servers. On the systems you want to remotely access, you also need to turn on Screen Sharing in the Sharing preference pane.
Once active, any remote computers registered to the same MobileMe account should appear in the Shared section of the Finder sidebar. The Finder combines computers available via Bonjour on the local network and via Back to My Mac over the Internet in the same list. If you travel, that can be both reassuring and a little confusing.
To access one of those computers, select it from the Sidebar list, then click the Share Screen button. (That button is in the upper right of Finder windows in all but the Column view; in the latter, it's below the computer icon). You should then be able to control the remote system's screen. If you don't see Share Screen as an option, the screen-sharing service isn't on in the remote system or there's a network problem.