In the past, I've been asked what the difference between Microsoft Office SharePoint Server (MOSS) and Windows SharePoint Services (WSS) was. In a nutshell, Server builds on Services, as you might imagine, but that doesn't really tell you what the true differences are. In v2, there weren't many, but a lot has been added to v3. With these changes, the difference between the two product lines has grown significantly. The main difference between the two lies within the enterprise features of Server, which ties multiple Services sites together with unified feature sets, like search, which is probably one of the most beneficial features. Of course, there's more to it than this, but you get the idea. Microsoft has a comparison of the different Server products, which is nice. If you're debating which you need, this is a great starting point. Mark Arend has just added to this by providing a comparison of what web parts are available in the Server and Services offerings . This comparison provides yet another crucial aspect to determining what feature-sets you'll need for your sites.