I came across a really useful tool the other day for generating sample relational data. It’s a web service called genereatedata.com (inventively enough). It lets you define the columns, data types, how to generate the data (such as random names, states, numbers, numbers in a range, and more), then generate the data. You can get data in a delimited form or even directly as INSERT statements for your database of choice. It looks like it generates 100 rows of your data for you for free, but that you need to pay for a premium service that is able to generate more rows, if you need it. Fortunately in my case I was good with 100 rows.
Of course, if you need to generate data for your cubes, you might want to use a tool designed specifically for doing so, such as the Cubedata tool I built some time ago (version 2 is in the works!).