As a matter or ethical use (and also to be in accordance with the license agreement) you do not point a performance testing tool, a class of tools designed entirely to destroy sites, at any site you do not own, manage, control or where you have permission from those that do have those attributes. If you consider the flights application insufficient then feel free to download any open source application and install it on hardware you own, manage and control.
Nothing stops you from pointing your tactical nuclear software at any website you wish, except for your willingness to agree to the terms of the license agreements for both your testing tool and the site that you are visiting. Although you may face legal issues if your IP address is tracked as a DDoS source..
GNU licensed CRM solutions, content management solutions (and various modules) should give your team ample items to practice with. When you feel they are ready, giv
e Stuart Moncrieff's scripting challenge a try at http://www.myloadtest.com/training/correlation-challenge/
James Pulley