A wise man once told me that the only general answer that suits all good questions, is the phrase "that depends." In the case of your good question, the only reason you would want to think about certifications would be if you wanted to get back into a more technical line of work.
If you want to stay on the management track, a master's in business, management, or engineering management would probably serve you much better than any technical certification would.
If you want to get back into something more technical, e-mail me again with your areas of particular interest and I'll be glad to make further recommendations.
This was first published in February 2002