Games you can play while chatting / learning / reading / doing stuff?

Greed Corp. It is a simple yet fun turn based game.

Uh.. Non-steam related, I play Anti-Idle: The Game (idle game hosted on Kongregate). That's what I play while idle/away.

Hector: Badge of Carnage 3-in-1 series, although it require some brain and you can't pause cutscenes.

Xcom(enemy unknown, or the older ones if you are into that) -> being turn based you can take your eyes off it without worrying of loosing important action
Heroes of might and magic -> ditto here.
or the new Divinity - original sin.This is a role playing game with turn based combat.
Otherwise a game I like to play while doing other things is Transport Tycoon Deluxe ( using OpenTTD), while the game is in real time, you can easily let it on by itself while doing other stuff, with the only thing that could happen is getting more rich :D

Pocket pool

Faerie Solitaire

Bloodbowl if yu disable the timer in options

Castle Doctrine, it just went out on Steam. Also most of the Paradox Strategy games. EU4, CK2 Etc.

roller coaster tycoon 1

Actually, once you have some hours in civ III PTW and the war stars, after you finish your turn, sometimes it takes like half an hour for your next turn.

Turn strategy games like total war(if you do autoresolve the battles) and civilization series.

You should buy the rougelike games bundle at Humble Bundle, three of them are turn based games and I find particularly good Swords of the stars: the pit.
King´s Bounty series is a good choice too (the 1st and 2nd ones at least).