From Disc Two's main menu, there are several simple eggs that can be accessed. However, you must be patient and let the menu run for some time in order to access them. Here's how the menu looping process works: The menu system will stand still for 30-second periods of time. Between these periods, one of three things will occur.
The first two involve the box in the lower left corner of the screen. In one instance, it will flash and say, "Join The Resistance". While it's flashing (which is only for a few seconds), navigate to the box by highlighting "Data Hub" and pressing left. Hit enter to view a message from "John Connor" explaining the DVD-ROM extras.
In the other instance, the box will flash and a circular image will appear in the box. Follow the same process as above to get to the box and press enter. You will now be able to view a T2-related Swelltone trailer.
The third Easter egg requires nothing on your part; the T-1000 will emerge from the menu and say, "Get out!" Nothing much, but a fun extra nevertheless.