2009 Merit Badge Changes
The following Merit Badges have had changes and revisions for 2009:
Visit this link to check what was changed: Changed MB Requirements for 2009

If you started the badge prior to revised 2009, you have the option of completing the badge using the old requirements or using the current requirements. If you haven't started the badge, you must use the current 2009 requirements.

2009 Changes
On August 1, 2008, the BSA announced changes to several merit badges which will take effect on January 1, 2009. New color merit badge pamphlets issued in August 2008 will reflect the new changes. Scouts may use the new requirements with the approval of their counselor, however, if they choose to use the older requirement, they should use the older pamphlet.

The following merit badges will have new requirements: Architecture, Automotive Maintenance, Cinematography, Coin Collecting, Collections, Drafting, Emergency Preparedness, Engineering, Farm Mechanics, Indian Lore, Insect Study, Landscape Architecture, Lifesaving, Motorboating, Painting, Pottery, Radio, and Swimming. To find out more about the requirements that were changed, visit: 2009 Merit Badge Changes
italic/bold denotes Eagle-required

Some other helpful links:

Steps to Earn a Merit Badge
1) Pick a Subject.  Read the requirements of the merit badges by reading the current Scout requirements handbook, the merit badge pamphlet or going to the Index to Merit Badges link and choosing the badge that you're interested in.  See Mr. Snyder and he  will give you the name of a person from a list of counselors. These counselors have special knowledge in their merit badge subjects and are interested in helping you and a are registered with the Council office. Send an email or phone the troop librarian to get a copy of the merit badge pamphlet. If the troop doesn't have a copy, you may need to go to the scout shop to purchase one. Get a signed merit badge blue card  from Mr. Snyder.
Scout Buddy System. You must have another person with you at each meeting with the merit badge counselor. This person can be another Scout, your parents or guardian, a brother or sister, a relative or a friend.

2) Call The Counselor Get in touch with the merit badge counselor and tell him or her that you want to earn the merit badge. The counselor may ask you to come and see him so he can explain what he expects and start helping you meet the requirements.

When you know what is expected, start to learn and do the things required. Ask your counselor to help you learn the things you need to know or do. You should read the merit badge pamphlet on the subject.

3) Show Your Stuff. When you are ready, call the counselor again to make an appointment to meet the requirements. When you go take along the things you have made to meet the requirements. If they are too big to move, take pictures or have an adult tell in writing what you have done. The counselor will ask you to do each requirement to make sure that you know your stuff and have done or can do the things required. Be in your class A uniform when you see your counselor.

Get The Badge. When the counselor is satisfied that you have met each requirement, he or she will sign your application. Give the signed application to your Scoutmaster so that your merit badge emblem can be secured for you.

Requirements. You are expected to meet the requirements as they are stated --- no more and no less. You are expected to do exactly what is stated in the requirements. If it says "show or demonstrate," that is what you must do. Just telling about it isn't enough. The same thing holds true for such words as "make," "list," "in the field," and "collect," "identify," and "label."