Topic: Generating 'exemplary data', has anyone written code for this?

I found a product on the web from EMS called 'MySQL Data Generator' which costs $65 and generates data directly into the MySQL database.
I'd like to grow as a Rails developer and thought there might be a routine out there that someone wrote that could be used inside a 'migration' to generate this.
I envisioned something like this:
There'd be an array with a list of values. The routine would describe a sequence for the number of records to be generated and then as each was being built it would process the array in a block as each record was built.
Has anybody made a stab at writing code that moved in this direction. I'd be grateful to take a look.
Thanks,
David