How to use \section*{something} without removing it from the Table of Contents?

I am trying to insert an abstract and acknowledgement page into my report. I want to suppress the (numbers in front of):

1. Abstract
2. Acknowledgment

part by using \section*. But by doing so, it is removed from the ToC as well. Is there a way to maintain an entry in the ToC, while at the same time preventing this?