Focusing on academically-oriented activities (i.e. certifications, addtional degrees, etc.) really won't help your case as an engineer - it only serves to solidify the stereotype of the engineering geek.
As an engineer, the biggest hurdle (assuming your GPA/GMAT is okay - and exceptional scores won't really help if the rest of your profile isn't that strong) is showing that you are a well-rounded person with strong interpersonal skills and/or leadership potential. Regardless of whether you're looking for a finance career or not, MBA programs really want to build a class of dynamic students - the environment, orientation and culture at most (if not all) b-schools is not at all like engineering programs.
How you show yourself to be well-rounded comes down to what you do outside of work, and examples from work you can use in the essays and interviews to show that a good chunk of your ability to progress in your career comes from your interpersonal skills.
Alex Chu
alex@mbaapply.com
www.mbaapply.com
http://mbaapply.blogspot.com