Another way is to just use subtraction:

  x = x + y
  y = x - y
  x = x - y

I originally learned about this while preparing for some interviews.

The funny thing, I find, is that in Python you can simply do this:

  x, y = 5, 10
  x, y = y, x

I was asked this question in an interview and I responded that you can do this. His response: "Python is weird."