We've just added SearchBox to the AppHarbor add-on program. SearchBox is a fully hosted and managed ElasticSearch full-text search service. ElasticSearch is incredibly powerful and fast full-text search software built on Apache Lucene.
SearchBox is still in beta, so only a free plan is currently available. The free offering is fully functional though, and you can experiment with all ElasticSearch features.
Using SearchBox in your AppHarbor-hosted application is incredibly simple, just add the add-on and follow the instructions for .NET apps in the SearchBox docs. The preferred .NET client for ElasticSearch is called
NEST (available on NuGet) and the NEST site has additional documentation. The SearchBox guys have also built a .NET sample app that stores documents in SQL Server and uses SearchBox for full-text search. To experiment with the app, just grab it from GitHub and push it to an AppHarbor application with the SQL Server and SearchBox add-ons provisioned, and you're ready to go.
Don't miss out on full-text search, faceting, highlighting and other advanced ElasticSearch features, provision SearchBox right now.