OS X (Leopard)
Basic stuff, but I always have to re-learn it.
1) Open Directory Utility from the Utilities folder
2) Click "Show Advanced Settings" to show the toolbar at the top, which includes "Directory Servers" and so forth.
3) Click on the "Services" icon.
4) Check the "Active Directory" checkbox and then click on the pencil icon (above the padlock icon)
5) Fill in the "Active Directory Domain" field with "oak.uvic.ca" and the "Computer ID" with the name of the machine (e.g. "braeburn")
6) When challenged for a username and password, fill it in with your OAK id.
7) Once bound to the OU (Organizational Unit) go to the "Administrative" tab (you need to "Show Advanced Settings" to see it) and unclick the "Allow Administration by:" checkbox to keep the riffraff out.
8) You're done. To log in to the machine, users will click on the "Other..." icon and log in using a NetLink ID.

N.B. Users that log in this way will have local home directories, but they will NOT have a local account per se. That is, they will not show up in the "Accounts" applet in System Preferences.

For Linux (specifically Ubuntu):
A package is available that provides excellent CLI and GUI tools to bind the box to Active Directory. In Karmic, install the likewise-open5-gui meta-package, and it will take care of everything else. The GUI is self-explanatory.