You will always get more than what you paid for, from Windows SharePoint Services 3.0 (WSS), a ton features and functionality all as free! You just need a licence for Windows Server 2003; even you can use SQL Express Edition as free for a wide range of small to mid-size businesses. This is the main reason that I love building solutions based on WSS.

We have also Office SharePoint Server 2007 (OSS), a great commercial portal and content management solution, but if you have enough experience architecting based on SharePoint, you will agree me that more than 70% of real business needs, can be implemented based on WSS and you don't need huge and great features of OSS.

Actually, I prefer to use WSS vs. OSS when you don't need more than 30% of OSS functionality. It's an old story: we are getting more than 70% of our requirements by less than 30% of system's capabilities. So you can develop some features that you need top of WSS and be away from bigger load of money, administrations, hardware requirements, and most important, training users to use OSS.

One of the most important features of OSS that might force you to use it, is advanced features of its search capabilities, as a solution you can use WSS Cross Site Search.

It's a product from Knowledge Worker Components, and support a lot languages included Persian. You can define custom scopes for search included cross site collection search.

You can also define custom properties for advanced search by a comprehensive optional operations included: And, Or, Begin, Included, Null and...

For details, take a look to snapshots below: