LimeWire uses HttpCore & HttpCore NIO extensions to power all of its uploads (and hopefully soon, all of its downloads). Sam Berlin, Senior Software Developer with LimeWire said: "HttpComponents has been a breeze to work with, and integrates seamlessly with LimeWire's custom NIO layer".
Apache Synapse uses HttpComponents HttpCore to provide completely non-blocking HTTP support as an ESB and XML Gateway. The Synapse development team has done a number of performance tests including loading up more than 2000 concurrent clients, resulting in 4000 concurrent HTTP connections in and out of Synapse - all with a fixed small thread pool and no loss of data. Paul Fremantle, chair of the Apache Synapse PMC said: "HttpCore is a key part of Apache Synapse - and absolutely essential to our high-performance HTTP support. The HttpComponents team have always been extremely helpful and the quality of the code speaks for itself".
Google Android ships with HttpCore and HttpClient 4.0 bundled.
JClouds provides concurrent apis to popular cloud services. HttpCore NIO powers JClouds' server-grade S3 connector, allowing non-blocking uploads of String, InputStream, File, and byte  data without expensive conversions.
The AdroitLogic UltraESB uses HttpCore & HttpCore NIO extensions as well as the HttpClient to build a high performance, feature rich, easy to use and lightweight ESB. UltraESB is the first open source ESB to offer Zero-Copy proxying coupled with NIO and Memory Mapped files, to offer extreme levels of ESB performance. Apache HttpComponents is a key component of the UltraESB and its SOA ToolBox, and utilizes the excellent Zero-Copy and NIO support features of HttpComponents NIO
The Apache ManifoldCF project uses HttpCore and HttpClient for many of its repository and output connectors. These are connectors to repositories like Microsoft SharePoint and OpenText LiveLink, as well as output connectors for Elastic Search and Open Search Server. ManifoldCF also uses HttpComponents libraries for crawling the open web.