My favourite/most embarrassing typo of all time is this 1996 cover of Ms. magazine, which misspells "feminism." As an editor, the irony makes the empathetic pain I feel even stronger.
Errors on the covers of major magazines and books are pretty rare, but Darren points to a recent one, a typo of "launch" on the cover of a new O'Reilly tech book, and back in 1983 even Time misspelled "control."
Of course I make typos and spelling mistakes here, but I do try to minimize them, and they're a lot easier to correct online than in print. Plus I don't have a proofreading staff, other than you my readers. And you sure let me know if you spot something.