How can I make Visual Studio 2005 call a WCF service?
Yes, using the wsHttpBinding will expose the service as a standard web service.
Yes you can.
If you have .NET 3.0 or 3.5 installed, you can add references to the WCF assemblies (System.ServiceModel.dll etc) which are in the directory "%WINDIR%\Microsoft.NET\Framework\v3.0\Windows Communication Foundation". Visual Studio 2005 does not include the svcutil utility that generates a WCF proxy, but you can download this (it comes with the Windows SDK), or use WCF without a generated proxy (e.g. by using the ChannelFactory<T> class).
Or you can add a web reference to a WCF service that uses the basicHttpBinding, as suggested by Jeremy Lew.
Just to prevent some from looking this up - you used to be able to download a CTP version of WCF extensions to VS 2005, but this has never gone beyond CTP see this thread
It is still possible to get these in non-ms sites, if all you wish is to try some stuff, but without a doubt the correct way is to either use basicHttpBinding and consume the service as a "normal" web service or move to Visual Studio 2008.