I like using Red-Gate Data Generation for mass row generation :). I find it it works really well, and gives me the flexibility by using the regular expressions and such.

EDIT: When I first used red-gate tool, I was really impressed. I used the tool on a database that had 100+ tables. With FK constraints, check constraints, and field names with familiar keywords like first name, last name, phone number, and the tool was able to take all that into account to generate data that made sense with lists for names, and using regular expression for phone numbers to generate 10 digit numbers. I told it to generate 10,000 rows. So it generated 10000 rows x 100 tables = 1,000,000 rows of data keeping all rules valid in less then 5 min. Really quick and impressive I must say :D.

- Mohit.