Chances are you didn't see the newest feature of Steam, the Steam Wallet, coming, but it's available now if you'd like to use it. The feature, which is in beta, allows you to pre-load cash into your account, much like how you can drop credits into your Xbox Live Marketplace or PSN "wallets." The weird thing about Steam Wallet is that it's pointless. As of now, you can still give Valve exact change for games. There's no need to funnel your funds into it.
But how much money can you drop into your account? According to the Steam Wallet page, you can pre-load $5, $25, $50, or even up to $100 dollars into Steam. The money can then, of course, be used to purchase any game or within a game that supports Steam transactions.
It's not hard to reason out why the Steam Wallet might exist. Younger users without access to credit or bank cards need a way to purchase content, and if stores were to offer Steam Wallet cards with these increments in the future? Well, that'd take care of the problem, wouldn't it? Also, a pre-piad card would finally make brick and mortar Steam gifting a reality. But just to be clear, though: as of right now, Steam Wallet cards do not exist and no plans have been announced.