“What is the difference between MOSS 2007 and WSS 3.0? Should we spend the money for SharePoint 2007 or is WSS 3.0 sufficient?”
This is a common question for organizations looking to implement a Microsoft-based online collaboration system. The basic answer is Windows SharePoint Services 3.0 (WSS) provides a collaboration foundation with a variety of features including a web-based portal, document collaboration, etc. and Microsoft Office SharePoint Server 2007 (MOSS) builds on WSS by providing several additional enterprise features.
The best way to understand the difference is to evaluate the additional features provided by MOSS. This article provides a good feature comparison.
I have implemented both MOSS and WSS-only solutions for a number of organizations and although WSS is nice and will work, if you can afford MOSS (or SharePoint Server 2010) I would strongly recommend it.