Some Games To Waste Your Time
Mortimer Beckett and the secrets of Spooky Manor

Burger Rush

Sources for trial game downloads:
Playfirst, BigFishGames, Reflexive, Oberon
Cybermind: Free Mastermind Clone
Cybermind, basically is a code breaker game developed by CyLog Software.
The aim of game is to guess the pattern of four colored spheres (in both color and order) out of eight colored spheres. After the each attempt you are shown with a number white and red pegs. White means, you have a right colored sphere in sequence but its place is wrong, and if it is red then both the color and place of the sphere is right. You have to guess the pattern in at most twelve attempts.
I do know if this game will increase your IQ, but I am sure it will increase your mathematical skills and off course you will spend a nice time playing it.
Since Cybermind is only under 2 mb and it is portable why not give it a go.
S.T.A.L.K.E.R. Out of Map Experience (Warehouse)
S.T.A.L.K.E.R. Shadow of Chernobyl is in my Top 3 games list
Although it has about 30 square kilometers playable area we still need more of it.