Certification

Hi,

I am interested in getting certified in any of the SAP areas, well is there any certification exam from SAP like NETWEAVER, BW, WORKFLOW etc which i could take up without the SAP classes and could someone explain me the process.

Should i always partner up with SIEMENS OR SAP LABS for taking an exam or could i directly take up any of the exams?

Best Regards,

prithvi