There are actually only a few easter eggs to be found in Episode 1. I myself didn’t find these, considering they’re absurdly hard to point out. So here they are, credit to the people who found them.

Barcode

During “Lowlife”, in the dark alley where you first use your flashlight, there’s a bit of graffiti coupled with a bar code. The numbers under the barcode are “24724″, which is the area code for Freeman, West Virginia.

Resistance

When guiding the citizens from one end of the yard to the other, you can see another bit of graffiti. This one has the formula for finding resistance, except the A is changed to the anarchy sign and the R is flipped backwards.

Radiohead reference

When Dog throws you and Alyx in the car into the citadel, if you look closely at the steering wheel, you can see the Radiohead Bear logo.

There you have it. That’s about everything you can find in Episode 1. Once again, I didn’t find these easter eggs, so I take no credit for actually pointing them out, although this article is my own work.