The wonderful thing about Mancala is not so much that it is the world's oldest game, and still a good one at that, but that the color of the pieces are irrelevant.
I've spent many a bored hour with a friend waiting in some remote location for another group to join us while playing Mancala. It's just so easy to make.
Pick up 36 stones around the same size, draw 12 circles on the ground, 2 rows of 6 circles each, and you're good to go.
Each move consists of picking up all the stones from one of the circles on your side and placing them one by one around the board or into your store as you go. At the end of the game, the player with the most stones wins.
2. Checkers / Lines of Action
Some people feel that they've outgrown Checkers by the time they've reached adulthood, but it remains a challenging and intense game for adults. And the best way to play is on a larger board, such as 10x10 or 12x12, which you can draw with a pen and paper. For checkers, you can use just about anything: coins, beans, cereal, chips, what have you.
It may take you a few games to remember most of the tricks, but it's only after you get those tricks out the way that you begin to start looking deeper into the game.
You can also play a number of other good games using a checkers board and pieces. Lines of Action is one of the most highly regarded of these games.
Diplomacy is the world's most popular negotiation game. Played by millions of people, including governments and militaries, for the last fifty years, it's a tense game of skill, bluff, and deceit. Don't play it if you're thin-skinned.
You need to move your pieces each round to control territory. Whoever controls the most territory by the end of the game wins. Simple enough; but no one can make any real progress without forming, and breaking, multiple alliances.
You can download the rules and maps for playing Diplomacy from the above link or from the official web site. All you need to supply is a pencil, a few hours, and preferably six very good friends.
These two print and play abstract games played on the same board are both highly rated on the Geek. They were invented by Adam Kałuża from Poland.
The contender for the world's oldest game is still the world's best game, and it can be played for free. You only need a large sheet of paper, a pen, and pencils of two different colors.
It's an abstract game, but it's so much more. As you place your marks trying to control territory, the areas of the game become alive.
The game has a different feel the first time you play from after you've played fifty or a hundred times. And its built-in handi-cap system let's any two players play against each other and enjoy a challenging game, regardless of relative skill levels.
6. Battle for Moscow
War games are a rich field of gaming. Unless hampered by a really bad rule system, every war game encompasses deep strategy and tactics, while simultaneously teaching significant historical lessons.
There are hundreds of free print and play war games online. Battle for Moscow is widely regarded as an excellent example of the genre.
BonusHere are some other ways to while away the hours and play free board games:
Almost every single game you can think of has been implemented for online play, and the vast majority of these are free to play. You can Google for your favorite game, or consult various lists of online games, such as this one.
Acquire Geek Gold
Board Game Geek's user contribution system gives you Geek Gold whenever you submit worthwhile content to their site. While this "gold" can be used for BGG perks, such as uploading an avatar, you can also trade it to other users for real-life games by checking BGG's auction pages.
Find a Game Club
Of course, the best way to play games for free, and to find people to play with, is to find a local gaming group! Not all gaming groups are free. Some are, and some charge token entrance fees. Many will be happy to let you come and try out the games.
To find local gaming groups, check out BGG's Game Groups forums.