Is it Traditional --> Roth or Roth --> Traditional?

If the Recharacterization is done before you filed your 2007 tax return, then you don't need to file any additional tax form.

For Traditional --> Roth recharacterization, you will not get any deduction on your 1040 this year.  If it's the other way around, then you will get a deduction if your AGI is below the threshold, 50K or so.  (Don't remember the exact number).