One possibility for an icebreaker would be to play Fizz-Buzz. Go around the group counting off, but if the number is divisible by 3 say "Fizz". If it's divisible by 5 say "Buzz". If both, say "Fizz-Buzz".
I've heard this described as a child's game, but I remember it as a college drinking game. Screw up, and you take a drink.
For a programming challenge, try writing code that prints out the Fizz-Buzz sequence. This is not really difficult, but it's a couple steps up from "Hello World". Implementing it requires students to write a loop, understand conditionals, and how to take the modulus of a number. Students who finish first can help out others who are struggling.
Fizz-Buzz has been used for screening job applicants. Take a look at:
http://blog.codinghorror.com/why-can...mmers-program/