WHMCS is generally regarded as one of the best (while still being affordable) billing and client management softwares for Hosting. There are also forum modules that can be installed to have integrated forums.
It doesn't really provide any frontpage management solutions for a full website though, there may be modules for that as well...not sure on that area though.
you aren't going to find any solutions similar to 1and1.com or hostgator for free, those are custom, in-house designed solutions that probably cost them thousands (if not 10s of thousands) to create.
I can't speak much to any free solutions, as I don't use them. But as far as WHMCS goes, there is a CMS module (paid) as well as a forum module (paid) that can be installed to turn it into a working CMS system with a little work.
Sorry I can't suggest more on the free side...just not that experienced in that area.