For me, it depends on the client.
If its a new client I state in my quote/proposal how many amendments they will get on a design before I start to charge my hourly rate.
If it is a long standing client I'm a lot more flexible.
It is a difficult one though, becuase changing a type face is different to having to change the whole nature of a background image. Again, I'm pretty flexible depending on the task asked of me, but I will inform the client if this is to take up one of their allotted changes or not.
I totally missed the poll part of this thread and only saw it after I'd typed my response. I went for 1-3 changes before charging.