The hero to the rescue for building strong multiple-choice test questions is the Contructing Written Test Questions For the Basic and Clinical Sciences manual produced by the National Board of Medical Examiners.
There are four sections that cover:
1) Issues regarding format and structure of test questions
2) Writing one-best-answer questions for the basic and clinical sciences
3) Extended-matching items
4) Additional issues (with appendices)
There is a PDF of the entire manual available. If you prefer not to print all 180 pages out at once, you can also view each section individually.
Faculty at the Univ of Pennsylvania School of Medicine also put together a 38-slide powerpoint presentation based on this manual and used it as part of a faculty development series.