WCF service without using certificates and win auth.

Hello everybody

 Could somebody tell me a possible configuration for a WCF service (ws or basicHTTPBinding) that supports authentication without certificates and without windows authentication. E.g. with a custom username/password validation?? I know that username/password travels unencrypted to the target service, but that is sufficient in my case.
I am also wondering if it is possible to implement a fully open WCF service (no authentication at all, like a fully open web service). Is this possible? 

Somehow that was much easier with good old Webservices in .NET 2.0...

 Thanks for your inputs!

Cheers
 Brad
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