For simple and fast interactive (zoom, rotate, etc.) displaying of a 3D model from a CAD application on a mobile device you can use e.g. the "Inventor Publisher Mobile Viewer" (IPM Viewer). This free application is available for Apple iPad and iPhone and for tablets and mobile phones based on the Android OS.
You can download IPM Viewer from the respective "Market" for your device (Apple or Android) or from www.cadstudio.cz/download
IPM files for this mobile viewer can be published from Inventor Publisher or from the Photofly web-cloud service (now "123D Catch"). Published .ipm files can contain not only the model but also its animation (e.g. moving parts, assembling), assembly instructions or other textual information to the presented product.
Inventor Publisher can process CAD data from Autodesk Inventor (iam, ipt), CATIA V4 (model, session, exp, dlv3) a V5 (CATPart, CATProduct, cgr), Pro/ENGINEER (asm, prt), Solidworks, NX, Parasolid, JT, DWG (3D), DWF, DWFx, STEP, IGES and SAT.
An alternative way is e.g. the 3D DWF format and its online viewer Freewheel - see the sample. Another option is the Glovius viewer (JT files).