Despite its flaws, namely that it isn’t exactly as anonymous as actual cash, the online only, cryptographically rooted currency, BitCoin, seems to be garnering more attention than any of its predecessors in the space. As Slashdot notes, it arguably has achieved greater actual success too attracting a considerable number merchants, markets and open exchanges (for converting BitCoins into other kinds of spendable currency). Last year EFF announced they would accept donations via the P2P system. (I followed their example soon after, see my support page for the details on BitCoin donations.)
The point of the Slashdot post, however, is to note that BitCoins have grown in value to the point where the most common exchanges now hover right around the one-to-one rate with US Dollars.