Overnet and eDonkey

aMule
Multi-platform eMule-like client forked from xMule.
http://www.amule.org/

eMule
Open source Windows client for the ED2K and de-centralized Kad networks released under GPL.
http://www.emule-project.net/

eMule Morph Mod
Presents a derivative of eMule with additional features, includes a support forum and a FAQ section.
http://emulemorph.sourceforge.net/

eMule Plus
Fork of eMule aiming to provide a fancier user interface.
http://emuleplus.info/

eMule Xtreme Mod
Presents a modification of the official client, the goal of which is to manage bandwidth more efficiently. Also includes detailed documentation.
http://www.xtreme-mod.net/

EmuleSkins
Features a gallery.
http://www.emuleskins.net/

FileDonkey
Search engine for files on the eDonkey file-sharing network.
http://www.filedonkey.com

Lphant
Runs on the .NET framework, able to handle BitTorrent, ed2k and Kademlia protocols. Adware.
http://www.lphant.com/

Peerates.net
Provides server lists, including verified, secure servers. Also offers various statistics about the eDonkey network as well as information on availability of files based on their ed2k hash.
http://www.peerates.net/

Razorback 2 Memorial ed2k Stats
Intended as a replacement for Razorback 2's statistical services, provides several data about a given ed2k hash or link such as the ratio of full copies, the number of total sources and the size and type of the corresponding file.
http://www.tothbenedek.hu/ed2kstats/

xMule
Multi-platform eMule clone.
http://sourceforge.net/projects/xmule