I do this all the time- when I'm writing emails, sometimes I type "Good afterboob". I mean, look at it! The "b" is right next to the "n"!
Ugh I do this kind of thing all the time. I don't know why my typos are so Freudian. I think the best one to date is my substitution of one letter in "floppy disk." I thank my lucky stars that was in an IM with a friend and not an email to my boss or anything
My favorite typo in a store award goes to the Walgreen's in Naples, Florida. One of the employees had made a sign to put on a stand advertising embroidered towels, but the sign said "embryoed towels." Yes, towels decorated with embryos. Now that would have been a conversation starter of a hand towel.