An engineer and armchair philosopher named Joel created this terrific bar graph of one-letter words that appear in Google's 8-trillion page index.  "A" is the most common single letter on Google, followed by "e," "i," "o," and "s."  At first I was surprised that "v" appears more often than the vowel "u," but then I figured it must have to do with "v" appearing as a Roman numeral.

I like how the letter index goes all the way to 30, as if there are slots available for letters that only appear in leap years or something.