I always thought it was a bit odd that Microsoft did not have a certification programme for just WSS and/or SPS but only combined with CMS, which in my opinion is too broad. Many of my collagues are experienced in Sharepoint or CMS and very very few (actually none) in both. Well for people like me, there is good news! Check out this post from Trika
Developer certifications for Office 2007
For Office, there will be three MCTS level certifications for developers, each requiring 1 exam. MCTS is Microsoft Certified Technology Specialist, which is the technology-series certification in the new format of certification. There is also a Microsoft Certified Professional Developer (MCPD) series that focused on job roles... but we won't have any MCPD for office. I think the betas for these three are scheduled for January (more on betas).
MCTS: Office SharePoint Services (MOSS): Application Development (70-542)
MCTS: Windows SharePoint Services: Application Development (70-541)
MCTS: Office 2007 Client: Application Development (70-543)
More on the new certifcation format here: official overview: http://www.microsoft.com/learning/mcp/newgen/default.mspx or here: from one of my friends/co-workers at MSL for interesting take: http://vishaljoshi.blogspot.com/2005/12/are-next-gen-certs-launched-to-make.html