The NameVoyager lets you type in a name and see the number of babies per million that name was given to from 1900 to 2003. Below is Alex. Note that the thickness, not the height, of the lines gives the relative use of that variant.
It’s unfortunate that the data only go as far forward as 2003 because obviously the popularity of Alex will have exploded after August 21 of that year.
Thanks to the Freakonomics blog via Amanda Agan for the pointer.