[glandium]

It was so common that "something cd key" was a common search term. And people would put that in the wrong input box/window such that they would end up typing that in chat rooms. In some of those, people would reply with the same "something cd key" followed with "to you too", as if it were some form of greetings. Later on, people would show up saying "something random cd key" as an actual form of greeting, not a mistake.

[Zircom]

Reminds how typing an album name into Google used to autocomplete to add MediaFire right after it.

[nunez]

or site:blogspot.com. (So many legit downloads on blogspot, even today, though most of those links are dead now :( )

[xtracto]

I remember serials.ws with its frame based we site... had all the keys you'd need. Also there was a windows program that was basically a database of keys and serials.

[ornornor]

Those were the days.

There was also that site with all the trainers and cracks for every game ever, with a little landing page that would dynamically show online and offline mirrors before it was cool. I forget its name but as a 10–14 years old I loved it.

[ornornor]

gamecopyworld.com it was called. I just remembered.

[nunez]

"______ serial" was my go-to on Google.