"Aoccdrnig to rscheearch at Cmabrigde Uinervtisy, it deosn't mttaer in waht oredr the ltteers in a wrod are, the olny iprmoetnt tihng is taht the frist and lsat ltteer be at the rghit pclae. The rset can be a total mses and you can sitll raed it wouthit a porbelm. Tihs is bcuseae the huamn mnid deos not raed ervey lteter by istlef, but the wrod as a wlohe."
I haven't found a link to the research (if there actually is any) but I did write a little perl script, scrmable, to test the hypothesis. It wroks pertty good!
I think the scrmabled words taht are least readable are the ones that end up with a lot of consecutive vowels, or that split the initial phoneme.
Update: March of teh Slashdorks!