I had one for my cousin a year or 2 ago, and had a bunch of activities. I was trying to include a wide range of things to appeal to everyone, trying to get older and younger people involved, etc.
First I gave him a list of things to have packed for the start of the day, just to throw him off and keep him guessing.
Rented a mini-van, picked him up, and a bunch of us met at a golf course to play 9 holes. Everyone was responsible for their own ticket.
Then drove back to my house where a bunch of other people were waiting. Had a big cookout, basketball, football, etc. Had a local sub shop and pizza place supply and deliver the food.
To help fund the event, and get some cash for my cousin for his honeymoon, I bought a crapload of random gifts. Various inexpensive tool kits, cheap CD players, Playboy DVDs, a 'mystery cooler' filled with steak, chicken, beer, etc.... I then sold raffle tickets at the cookout. At the end of the day, we picked tickets and the winners chose their prizes. It was a load of fun, and we made a bunch of cash.
After that we hit the bars, etc.
Next day we went to a baseball game. That was probably the worst part of the deal - everyone was so hung over, it wasn't as much fun as it could have been.
Good luck!