I'm not sure what to do here. I bought several games, non of which where I received emails or anything pertaining to multiplayer authentication keys. I emailed GOG and haven't received a reply. Did I just waist my money on this place?

Normally if there are keys available they are in the library just under the download links :-)
But best would be to tell us what games you are actually talking about.

[edit] Here is also a thread with information about which game have serial keys and for which games you need to contact support because they are not automatically included:
http://www.gog.com/forum/general/gog_games_with_serial_numbers

What moonshineshadow said. Also check out this thread, which lists the games that need serial keys for multiplayer and where to find them. I think the list is incomplete though.

EDIT: Ninja'd

Who/where did you e-mailed ?

Such a negative attitude.

Hey guys, I just realized what a complete dumbass I am. It's in my library, thanks!

Welcome to GOG! 8)

Hahaha welcome to gog Mr Dumbass Sir! :P

HEY HEY HEY!

There's only room for one dumbass here and I'm not about to leave!

You could work in shifts.

But tiny already takes most of the timetable by himself, there really might not be any place for a new dumbass

Hail Cthulhu!!!

Perhaps make it a time share.

Welcome to GOG. I think you will fit right in here ;-)