Activity based small groups are a great way for people to get to know each other.  Because of the activity that brought people to the group everyone starts out with something in common they can talk about and it can erase the need for ice breakers.  Activity based small groups can cover just about any activity or sport that people enjoy and it can be thought of or called a club instead of a small group.  For example:

Biking:  The people in the group get together once a week to go on bike rides together. 

Camping:  The members of the group get together once a month to try new camping locations. 

These groups are great for making connections and building friendships, but the sometimes don't go as deep because it can be more difficult to get good solid discussions going with the whole group, depending on the activity.  Something like camping, for example, would be very condusive to great discussion times.  Something like biking, on the other hand, probably wouldn't lead to as many good group discussions.

One suggestion we have is that if there is a group that doesn't lead to good discussions or spiritual growth, then at least once a month when the group meets have a more intentional Bible study and discussion time instead of the activity.