The best place to find reputable WordPress themes free for use is the official WordPress theme repository. Every theme in the official repository is licensed under the GPL, which means that you can download it, modify it, and distribute your changes as you please.
You'll find themes for almost every use in the repository. There are themes for business sites, blogs, and even team communication. If you look hard, you'll probably find a theme you can use, or at least one you can modify to look the way that you want.
A web browser with Internet access is required to download themes from the official theme repository.
First fire up your browser and visit http://wordpress.org/extend/themes/ ...