This question can be answered by the following questions and a little research:
Server OS (Mac OS X, Windows, Linux, etc)
Platform (Perl, Python, PHP, ASP.net)
Database (MS SQL, mySQL, Oracle, etc.)
Once you have those specifics, do you want to pay for it or are you willing to use Open source.
Many of my friends and colleagues use Plone which has many advantages such as inter-platform operability and compliance with government standards for accessibility guidelines, etc. It's two major downsides are the learning curve and there has been some minor concern that it gets sluggish when you scale it to large but that last concern is not confirmed.
I would do a little homework to find one suitable to meet YOUR needs.