Well I'd say that most people write their own code to run reports from their data as it will mostly be specific to them. There are however a number of charting things that plug into a rails app quite easily.
There is also an apress book called Practical Reporting with Ruby and Rails which might be worth a look.
Good luck.
EDIT:
If you want to paginate data then will_paginate is the standard gem/plugin used by Rails developers, it's great and easy to use. For export to other formats there are several options. For PDFs there is Prawn, PDF::Writer or HTMLDOC, Prince is excellent but not free, but I think there is someone porting it to an open source library (if I remember right), and there are several libraries that can help you easily export to CSV files as well.