my list of social free things to do with friends that comes to mind
Free sports in parks: volleyball, tennis, fishing, bike riding, baseball ect
Go dancing, there are many bars and clubs that are free to enter, and your not forced to buy drinks
Swimming in the ocean or lake
Cook together and enjoy a great meal as a group
Exercise together, running, biking, swimming or at home exercise videos
Play games: pictionary, cards, Wii, ect.
Mud Wrestling: (had to throw one goofy one in)
Brew tour or Wine Tastings
Dog walking