I am planning a SSO implementation using SAML 2.0. It is going to be SP (Force.com) Initiated authentication. I wanted to know if any SSO IDP simulator is available from AppXchange (preferred over Java based tools) to understand the implementation before trying it out with Enterprise IDP (ADFS in my case).
You can set up another Salesforce org (e.g. a developer edition) to be your IDP - that's how I got to grips with it originally. There's a wiki article that guides you through the whole process at: