Creating unnumbered parts/chapters/sections (plus adding them to the ToC and/or header)

I'm using the report document class for a thesis, and I need to add things like "Acknowledgements" and an "Introduction". I noticed that there is an \abstract command which would have been wonderful if applied similarly. How do I add these without messing up the chapters' numbering while being picked up by the ToC in proper order and page numbering?