We've had good sucess using joomla. We use J!WHMCS integrator to keep WHMCS and Joomla integrated. It syncs logins and designs. Very good addon. It is a tad pricy but if you use all of the features, it really does work out well.
We use Joomla! for our site, along with WHMCS*. Looked at J!WHMCS, but in the end opted for re-writing the Joomla! template to work with WHMCS.
The whole thing works great!
I don't think anyone will bother writing a WHMCS-like module for Joomla! to be honest - and even if they did chances are it would be nowhere near as good, or free.
*We just moved to WHMCS - previously we used HostBill and this also worked very well when integrated with Joomla!.
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Well, not exactly - as far as I know, there is no web hosting module for Joomla. That doesn't mean that it can't happen though. I've seen some places run a web hosting company using a custom made Wordpress module and ZenDesk and it appears to work like a charm.
I don't recommend using Joomla though unless you anticipate on having a large website and plan on making changes a lot like GoDaddy or another big company does. In my opinion, JWHMCS is also the best solution currently available for a web hosting billing system and it utilizes WHMCS.