Few months ago I wrote a question on oracle-l regarding generation of test data. Stephane Faroult answered me suggesting to take a look to the fourth chaper of his own book Refactoring SQL Applications.
Having test data is really important because many times you cannot work with masked data or you do not have any data at all.
In my case I had to generate a table, huge table, of employees or citizens. The solution was to find and download lists of firstnames and surnames with rank and distribution; also I needed a list of top1000 cities in the United States. Google is always an interesting source, but the best site is, for US of course, the Census Bureau website.
Stephane Faroult suggested a method to calculate the frequency based on rank and then to create a table with correct percentage of names. The book contains a set of scripts can be used and adapted for any needs.