Found in the Boiler room in QE
Only real computer nerds like myself will get this. All of the keyboards seen throughout the game are actually based off of the IBM Model M keyboards.
And not sure if this has been mentioned, but if you listen closely to the scientists arguing here in Anomalous Materials, you’ll find that it’s a reference of the production of Black Mesa and how it’s just a remake and not a full game. That one made my day. :3
Not sure if it was mentioned, but one of the levels has a bunch of scrolling text, including some from a New Scientist website.
I think now that the game takes place in 2006/2007ish.
Looking through the screenshots someone linked earlier, I noticed this one.
https://picasaweb.google.com/HughJundys/BlackMesa#slideshow/5791842439086730338
It’s a reference to Pixar’s Monsters Inc.
I think this could be the cat that was used in place of the areas blocked by closed doors, before they were fully mapped out.
These are really funny. I really need to start looking.
I for one really, really hope that when the last part of BMS comes out with Xen etc. that the devs fill it full of easter eggs and other stuff. I doubt we’ve found everything here yet either. I think I’m going to have to crack out the old boredom cap and search every inch of this game.
Man, I felt SO proud of finding the Hat in the warehouse during Lambda Core that I took it with me just because it was my trophy. I’ve never found achievement related super hidden goodies like that in a game before all by myself.
I ended up leaving it on a shelf in an office due to the frustration of the teleport puzzle while carrying it and figuring I was being silly trying to take it all the way to the end… little was I aware there really WAS an achievement lol.
if you “Use” the Schroedinger’s Cat Picture, It disappears.
I had to go try this. Took forever to find a Schroedinger picture (couldn’t remember where I’d last seen it), but once I found it, I realized it does the same thing as any other framed picture that you can “pick up” off of the wall. If you’re standing too close when you grab it, it clips into the wall and seems to disappear - but as soon as you back up or turn to the side, it’s in your “hands.”
Unrelated:
I doubt it’s an easter egg - but I’m not sure if it was intentional, a glitch, an oversight… (or maybe even just some random anomaly on my particular machine). But anyway, I found that the movable TOW missle crates found later on are as light as a feather and kind of float back down when you throw them in the air.
I can’t find this lonely scientist…
Look what I found. 
Double nostalgia!
hah you are the first one to point that out. I was wondering when someone would.
This part is brilliant, I noticed it and it’s the icing on the cake (which is a lie, yes yes yes).
The “Temperature Analysis” panel on Blast Pit’s rocket-engine control-console shows some text that, upon searching for said text on Google, reveals that it is the lyrics to the chorus of [‘Daisy Bell (Bicycle Built for Two)’ - Harry Dacre], a song dating all the way back to 1892.
Step 5: Get disintegrated by particles that have yet to be named by human science. Oh, sorry. “Saiens”.
Credit for the picture goes to aNILEator.
I saw this on a notepad in Questionable Ethics, as well.