What are the 'free to use' workload generators available for Oracle?
Lazer,

Here are what I have found: Load and Performance Tools. This is a huge list of tools, you can find out what product is better for you, but I could not see any tool that has been created specially for Oracle databases (on my first sight). For Sql Server

An information resource for software testers

I hope it will help you.

ADDED:

The best generator that you made yourself.