The best man will normally be the one to handle all of the planning of the bachelor party. Although all of the other groomsmen should help with some of the planning and payment for the party. As the best man make sure that you take into account of what the groom wants to do without fully giving away all of the details of the party.
Traditionally this is the last night that the groom gets to let loose before taking the plunge and becoming a married man. Below I have put together a list of ideas and events for your bachelor party.
Go to a nice comedy club and have a few drinks and a nice dinner
Watch a magician show
Rent a limousine and tour a city and all of its sites
Take a weekend away and go hunting or fishing
Go on a ski trip
Go to a ball game and rent a hotel for the night
Go play paintball with all of your guy's
Take a nice golf trip
Rent a lakefront cottage for the weekend
Take a road trip and visit all the places you have dreamed of seeing
Take a tour of the White House
Rent go carts for the afternoon
Have a poker night out and a few brews to go along with the poker and cigars
Rent a basketball gym and play basketball
Just remember that this is the grooms party and make sure he is having fun and enjoying his self and please do not humiliate him in any way.