Keith Elder nicely compares ASMX to WCF here. Check it out.
Another comparison of ASMX and WCF can be found here – I don’t 100% agree with all the points there, but it might give you an idea.
WCF is basically “ASMX on stereoids” – it can be all that ASMX could – plus a lot more!.
ASMX is:
- easy and simple to write and configure
- only available in IIS
- only callable from HTTP
WCF can be:
- hosted in IIS, a Windows Service, a Winforms application, a console app – you have total freedom
- used with HTTP (REST and SOAP), TCP/IP, MSMQ and many more protocols
In short: WCF is here to replace ASMX fully.
Check out the WCF Developer Center on MSDN.
Update: link seems to be dead – try this: What Is Windows Communication Foundation?