I am a Taiwanese national, and have been on H1B since 2006.

Which Tax form should I use ? Am I classified as a resident alien or non-resident alient..

Thanks.

Hi,

I'm almost sure you should be considered as resident alien. As H1B visa holders normally are not exempt individuals.

Please refer to Substantial Presence Test: Substantial Presence Test

On H1-B your days in the U.S. count toward residency.
For 2008 you MUST file resident tax return Form 1040EZ or 1040A or 1040. Also in 2007, you were resident.
Read about H1-B tax filing: Your U.S. Tax Return: The U.S. Visas

There is no such thing as taiwanese national. You are called CHINESE!! In every single sense. D***head