Best Free Web hosting service

Hello,
I am looking for a good free or low cost web hosting service to launch a website for my new company. It will take us a couple of years to break even so I am looking for a free or a low cost provider.
In terms of space, I will be uploading a lot of photograph based powerpoint presentations. I also want to maintain a database of visitors to the site.(users will have to register to view certain sections of the site).
Low server downtime is my other main concern. Pls advise.