Hi Prasanna,

If by certification you mean certification for yourself as a developer, there is the "Microsoft Certified Technology Specialist: Windows Mobile 5.0 Application Developement" certification. To obtain this you need to pass MCP exam 70-540. See the Microsoft website for further details on what this exam covers etc - Preparation Guide for Exam 70-540: TS: Microsoft Windows Mobile 5.0 - Application Development

If by certification you mean certification of your products, there is the Designed For Windows Mobile logo certification process. You can find out more details about this process on the Microsoft website - Mobile2Market: How to Participate

With respect to suggested architectures etc, you may like to review some of the samples/reference designs developed by Microsoft, some of the more popular ones are:

Mobile Client Software Factory (MCSF) - patterns & practices - Smart Client Guidance - Home

Mobile Line Of Business Solution Accelerator - Download details: Mobile LOB Solution Accelerator

An quote from the Mobile Client Software Factory website:

The Mobile Client Software Factory provides integrated guidance to help architects and developers create line-of-business Windows Mobile applications that interact with back-end systems over networks such as WiFi and GPRS that might be intermittently available.

Hope this helps,

Regards,

Saravana