Full text search engine with Redis. Works in all Ruby projects. Very simple built, source code is < 300loc including tests. Was built because it's cheaper to go with the 20mb Redis solution with redis than using PostgreSQL's full text search. Also I needed background jobs and might as well use Resque for that.
Gemfile gem 'Rfizzy', '~> 0.1.0'
install gem install Rfizzy