AndAR Model Viewer is an Android application that is capable of displaying 3d models(wavefront obj) on Augmented Reality markers. Go to the project's website for detailed instructions.
Try out the app called "AndAR" first, to see if your phone is supported.
Please report any bugs on the website:
http://code.google.com/p/andar/
supported on:
Nexus one/HTC Desire
T-Mobile G1/HTC Dream
Motorola DEXT
HTC Legend
HTC Hero
HTC Magic
... and many others