Skin the sausage
Ask your group to form lines of equal numbers of people, (if you like getting competitive you will need at least two groups). Each group then forms a chain by reaching back between their legs with their left hand and taking hold of the right hand of the person behind them. The person at the back of each line then crawls through everybody's legs, without letting go, and the rest of the line follows. The first line to make it right through to the front without letting go 'wins'. If there's only one team there is no winner as such unless you want to play against the clock.
There may be a problem if girls are wearing skirts....
Doctor Doctor
Ask your group to form a close circle, facing inwards and shoulder to shoulder. Then they close their eyes, reach their hands out and grab two other hands. (Check that they are holding two different hands and not that of someone beside them - rearrange if necessary). They then try to unravel the knot without letting go, (working slowly and carefully and not pulling arms out of sockets!). There may not be a single circle - there may be 2 or more and these may be interlinked, and that's fine!
Circle knee sit and walk
Have the group stand in a tight circle with everyone facing the back of the person in front of them. On the count of 3, everybody sits down very slowly. They will end up with a circle in which everyone is sat on somebody else's knee. If you have managed to get them this far the next bit is easy... on the count of three everyone starts to 'walk' slowly round in the circle and in time with each other, whilst still sitting on laps. The 'fallout' from this can be painful.... be careful!