New Scientist has a feature on five conceptual successors to flash memory. These are all technologies currently under development that could fit terabytes of information on a single tiny chip—and some of them aren't too far off.
The five here considered are MRAM (using two thin layers of magnetic material), FeRAM (which creates polarization through ferroelectrics), PCRAM (using lasers, sort of like with CDs and DVDs), RRAM (a variation on PCRAM that uses electrochemical reactions instead of heat-induced changes), and Racetrack (which, frankly, I understand even less than the other four, hard as that is to believe). If you're not a sciencey type, descriptions of these technologies may sound like adults in Charlie Brown's world, but they could be the next revolution in data storage—so read up. [New Scientist]