emule

eMule is a free peer-to-peer file sharing application for Microsoft Windows. Started in May 2002 as an alternative to eDonkey2000, eMule now connects to both the eDonkey network and the Kad network. The distinguishing features of eMule are the direct exchange of sources between client nodes, fast recovery of corrupted downloads, and the use of a credit system to reward frequent uploaders. Furthermore, eMule transmits data in zlib-compressed form to save bandwidth.
eMule is coded in C++ using the Microsoft Foundation Classes. Since July 2002 eMule has been free software, released under the GNU General Public License; its popularity has led to eMule's codebase being used as the basis of cross-platform clients aMule, JMule, xMule, along with the release of many eMule mods (modifications of the original eMule) on the Internet.
As of August 2013, it is the second most frequently downloaded project on SourceForge, with over 665 million downloads, only behind VLC media player.

What is eMule?
At dawn of  May 13th 2002 a guy called Merkur was dissatisfied with the original eDonkey2000 client and was convinced he could do better. So he did. He gathered other developers around him, and eMule Project was born. Their aim was to put the client back on track where eDonkey had been famous before, adding tons of new features and a nice GUI. They couldn't imagine what impact this decision would have...
As of today, eMule is one of the biggest and most reliable peer-to-peer file sharing clients around the world. Thanks to it's open source policy many developers are able to contribute to the project, making the network more efficient with each release.

What does eMule mean?
The name "eMule" comes from an animal called "Mule" which is somehow similar to a donkey ;)

How often is eMule updated?
eMule is not updated regularly, but at the moment the frequencies are between 1 and 3 months. Don't take this for guaranteed. :)

A list of a few features available.

• Clients use several networks to create one reliable network. (ED2K, Source Exchange, Kad)
  • Kad is now in an open testphase, eMule v0.42 can be enabled to use Kad
• eMule's Queue and Credit system helps to ensure that everyone will get the file he wants by promoting those that upload back to the network.
• eMule is completely free. eMule is also completely free of any Adware, Spyware, and ect. We do this for fun and knowledge, not for money.
• Each file checked for corruptions while downloading to ensure an error free file.
• The eMules Intelligent Corruption Control helps to speed up the correction of corrupted parts.
• Auto priorities and Source management allows you to start many downloads without having to monitor them.
• The Preview function allows you to look at your Videos and Archives before they are completed. For video previewing, we recommend the Video Lan Client.
• The eMule features webservices and a webserver that allows you to have quick access to and from the internet.
• You can create categories for your download to organize them.
• To find the file you want, eMule offers a wide range of search possibilities which include: Servers (Local, and Global), web based (Jigle, and Filedonkey), and Kad (Still in Alpha).
• eMule also allows you to use very complex Boolean searches that make the searches much more flexible.
• With the messaging and friend system, you can send messages to other Clients and add them as friends. In your friend list, you can always see if a friend is online.
• With the build in IRC client, you can chat with other downloaders and chatters around the globe.