As there are now Visual Studio Achievements, I used the available API and built a Windows Phone application around it, that allows achievement tracking and comparison. Details here.
I am currently looking for beta-testers. If you want to participate, shoot me an email to ddelimarsky $at$ live.com with the Live ID email you have associated with your Windows Phone - would appreciate any feedback.
PS: You don't need to be a registered AppHub developer or have a developer-unlocked Windows Phone to be a part of it.