Are there any good billing software that will allow for VPS provisioning? I'm thinking of using WHMCS but it doesn't seem to have any VPS server modules.

It has. WHMCS has HyperVM module and lots of others.

How about virtuozzo or any other VPS modules?

for virtuozzo you would have to use the paralelles billing suite as far as i remember, for hypervm you can use AWBS which is the best billing system on the market at present

WHMCS can provision VPS using HyperVM automatically. However, there is also a more advanced HyperVM module made by WHMCS client. I believe that module made by the client was a paid version.