MS professional certifications have been revamped for the .NET 2.0 cycle. When hunting around the certifications site, I remember coming across this picture / block diagram of the new certs available. However, it's not link from any of the top level pages, only from the "related links" section of the new generation certs.

Anyway, it shows the relationship between MCTS, MCPD / MCITP, MCA (Architect).

The New Generation of Microsoft Certifications: "The new generation of Microsoft certifications is more specific and targeted to reflect the detail of what you do and to prove your expertise"