FYI a recent post from the Excel team:
If you're new to Excel Services and are looking to understand what the product can do for you, these four training courses are a good introduction. Note that these courses don't cover the breadth of functionality in Excel Services, so I recommend supplementing this material with additional books, blogs, etc. on Excel Services if you are interested in learning more.
- Excel Services I: The basics: Use Excel Services to publish an Excel 2007 spreadsheet to your SharePoint site, where multiple people can access the spreadsheet at the same time by using their Web browsers. This course, the first in a series, introduces you to the basics of Excel Services, which is a part of Microsoft Office SharePoint Server 2007 Enterprise.
- Excel Services II: Requirements, recommendations, and permissions Learn the requirements for using Excel Services and how permissions can be set so that some people can edit spreadsheets, while others can only view them.
- Excel Services III: Control what people see Control what people can see when you use Excel Services to publish an Excel 2007 spreadsheet to your SharePoint Server 2007 Enterprise site.
- Excel Services IV: Allow user input Allow people to enter data for selected cells when you use Excel Services to publish an Excel 2007 spreadsheet to your Microsoft Office SharePoint Server 2007 Enterprise site.
Recent EPM posts on Excel Services: