Sharepoint 2010 Web Services on MSDN

http://msdn.microsoft.com/en-us/library/ee705814.aspx
http://msdn.microsoft.com/en-us/library/ee556847.aspx

Custom web services in Sharepoint 2010
http://sharepointbergen.blogspot.com/2010/02/creating-custom-web-services-in.html
Sharepoint 2010 Excel Services - Web Services
http://blogs.msdn.com/b/excel/archive/2010/01/06/updated-excel-services-web-services-api.aspx

Sharepoint 2007 - MOSS 2007 Web Services
http://www.decatec.it/blogs/2007/05/10/Sharepoint+2007+Web+Services.aspx