I was searching a lot for tools which can generate reports for me in sharepoint for many requirements like site usage, find the modified item in a document library, who all have modified a document in a document library, who had mad changes in the site..
The final answer on how to acheive all the same was simple.
Use Sharepoint Designer 2007
Yes, you can generate all the reports, create charts and even export them to excel from the sharepoint designer 2007. Open your site using sharepoint designer and at Site -> Reports, you can find almost all the options you are looking for......
Find this how to Article with more details.