In Visual Studio 2010, the empty “ASP.NET Web Service Application” projects are gone.
This is probably because Microsoft rather has you use WCF, so a few of those “older” templates are now gone:
To simplify things a bit in 2010, we’ve removed a few of the older templates. You can get the same thing by creating an empty website and adding a web service to it.
Funny though, as the “old” templates are still mentioned, of course in their ASP.NET 3.5 web service documentation, but also in their Visual Studio 2010 ASP.NET Web services documentation :-)