I'm research on web hosting and need find more information about non-profit 501(c)(3) web hosting. What are features include free hosting?
It's the exact same as a normal shared hosting plan. http://dreamhost.com/web-hosting/ has details on what's included.
Addons (additional domain registrations, unique IP, SSL certificates, VPS hosting, dedicated servers…) are still charged for normally.
I have a related question.
Does this mean you can register with a non profit for free and then since its unlimited domains you can also host sites that aren't nonprofit?
No, non-profit accounts are only for use for hosting domains related to the non-profit that the account was created for. If you need to host other domains, you will need to open a separate account for that.