StackedOff is an offline Stack Exchange site indexer and search engine. It's intended use is for people who wish to access Stack Exchange Network site(s), e.g. stackoverflow.com, but do not have a reliable internet service. StackedOff uses the 'stack dump' data files made public by the Stack Exchange Network.
StackedOff is available for free under MIT license here: https://github.com/tools4j/stacked-off
Some screenshots:
Search:
Question view
Selecting a site to index: