Does Saleforce.com provide Web services to access its objects? If yes,

What is the URL to get the WSDL from salesforce.com.

I have a requirment to develop BIRT report with salesforce data. BIRT provides a way to 

retrieve data from Web services when you provide an URL to the WSDL descriptor. 

I am hoping SalesForce provides access to its objects as Web services.

Thanks for your help.

Regards,

Raj