Rchart is ruby port of the slick pChart charting library.
Some of images are listed below which is developed using rchart.

acts_as_flying_saucer is a Ruby On Rails plugin that allows to save rendered views as pdf documents using the Flying Saucer java library. More info refer Pdf Generation Using Flying saucer Or Refer

It is a ruby Wrapper of jodconverter Which is used to convert office format to another office format.
It requires Open Office and java

Nailgun is server that preloads JVM so no need to load JVM on each request. Nailgun is a ruby wrapper of nailgun server and it's command.
Nailgun improves performance of standalone java application.
acts_as_flying saucer and convert_office both plugin has nailgun support.

Pasco is a gem that reads ie histories on providing ie history file i.e *.dat. It will return an array of object that contains url,modified_time,access_time,file_name,directory,http_header

safari_plist is a gem that reads safari histories on providing safari *.plist file.
It requires plutil binary. It returns array of object containing url,acces_time,visit_count