ProDoD is a simple program that lets you download all the Steam games freely from valve servers.
The games available to ProDoD are the most popular, like Counter Strike Source, Day Of Defeat Source, Half-Life 2, Half-Life 2 DeathMatch and many more.
All the games you download with ProDoD are downloaded from 51 and 57 servers. But you must remember that to be able to download the games you need to register on the Steam website (you need the CD-key for the game you've bought to register) and install it in your PC.