When you have an Office 365 environment, you can decide to create a public facing site, meaning that your visitors won't need to be authenticated to visit this site.
This public facing site will most of the time show information about your company, describe your services etc...
By default, the public facing site looks more or less like this
If you have enough permissions, you'll be able to amend the logo, the company name and a few other information.
After a while of struggling, I could eventually benefit from an Office 365 environment for which I had already developed a solution. The first thing I did was of course to test my solution with Office 365.
First, a bit of history : I developed a rating solution for SharePoint 2007 & 2010 (Foundation) and I've been asked recently to embed that into a SandBoxed solution.