A free way to control your Mac OS X hardware using a VNC Client (which is built into the newer versions of Mac OS X). Exciting, I know.

Top Left, click on the Apple and then System Preferences and under Internet & Wireless you'll find an icon labeled Sharing, open that.

Now click on Screen Sharing to select it and notice the users that will have access (by default it selects the group Administrators of your Mac which prevents non-Admins from connecting to your Mac. I suggest leaving this setting as is)

Final step of setup is to click on Computer Settings so you can set a password. So click on VNC viewers may control screen with password.

Now you are done with the setup part. Now you are probably wondering how you control this machine from another VNC enabled machine. Well if your other machine is a Mac OS X (10.5 or newer) then you can simply click on Finder (the smiley face) and click Go and then Connect to Server...

Note: You can click on the + button to add it below as a favorite. Click Connect from your remote Mac when you are ready to connect to the Mac you setup Screen Sharing on. Enter the password you entered and you are now remotely connected.

If you have Tiger (10.4) then follow these instructions at this site to setup your screen sharing in Tiger.

High level is this on Tiger (10.4.x)

1. Open System Preferences.
2. Select Sharing
3. Note: Services - Firewall - Internet (you'll first want to be in Services)
4. Turn on Apple Remote Desktop under Services
5. This will force a sheet to drop down. Turn on VNC and give it a password. You will need this password each time you log into this Mac
6. Be sure to Open the firewall to allow VNC traffic to come in so click on firewall, then place a checkmark next to Apple Remote Desktop.

Now you should be able to connect from a VNC enabled machine.

Note: if you have less than 10.4 then you'll need to either upgrade or get a third party vnc software pkg because vnc isn't built into the os until 10.4and newer