Microsoft Learning has a handy portal site up that has lots of information about SQL Server 2008 training and certification. There are book discounts, training discounts, free E-Learning offers, and an improved Second Shot promotion. A particularly useful resource is this PDF document that outlines all of the SQL Server 2008 Technology Specialist and IT Professional certification paths that you can take.
I have always been a big proponent of Microsoft Certification. It is certainly no substitute for hands on experience and knowledge about a product and technology, but I think that it is a very useful complement. Getting certified shows that you have initiative and care about your career. Most people will learn techniques and portions of the product that they may not have been exposed to previously while they are studying for their certification tests.
From a purely practical perspective, having Microsoft Certifications on your resume will often help you get job interviews. Having the certification can also be useful during the technical interview process for two reasons. First, it gives you more confidence that you know the product, and second it typically works as a passive form of self defense during technical screening interviews. The person(s) interviewing probably won’t be certified, and they will tend to assume that you are an “expert” because of the certification (which may or may not be true). This usually means that the questions you get will be easier. It is similar to how bullies avoid picking on someone who has 18 inch biceps, looking for easier prey instead.