Idea from this blog:
I've experimented with many types of interviews, but one thing I really dig lately is code reading. I print out 10-15 code snippets (not just code, but also UNIX commands, regular expressions, SQL queries and many other things). I then go through and ask: what does this snippet do, how does it work, are there any bugs, etc.? Reading code (as opposed to writing) means I can cover a lot of ground extremely quickly, spending no more than a minute or two on each problem.