There is no associated website but, for any questions or doubts, the representatives can be reached at their email addresses: 
christian.wessel@desy.de (Posdoc) and  sascha.dreyer@desy.de (PhD)

Their objective to discuss all aspects that contribute in a broad sense to the future of the research field of particle physics. Their homepage is here and the full mandate is available here

The young DPG adresses students at schools and university to give guidance in studying and career decisions. Please find the webpage here.

The early career communities of the ALICE, ATLAS, CMS and LHCb collaborations form together the LHC early career scientist fora to organize joint activities for non-tenured scientists among the LHC collaborations.

ATLAS Early Career Scientist Board

The ATLAS Early Career Scientist Board regularly organises events to socialise and provide a platform for exchange for scientists at an early career stage within the ATLAS collaboration. It also organises the ATLAS induction day in the context of the ATLAS software tutorial to introduce new members to the collaboration. For more info, see the webpage of the ATLAS ECSB.

CMS Young Scientists Committee

The Young Scientists Committee (YSC) represent the untenured researchers of the CMS experiment in the collaboration and management boards. It ensures communication between the young scientists and the management boards as well as organises career, physics, and social events for young members of the CMS experiment.
You can find the webpage of the CMS young scientists committee here.

yHEP is an association in the areas of particle physics (KET), astroparticle physics (KAT), accelerator physics (KfB), and hadron and nuclear physics (KHuK) with the goal of representing and coordinating the interests of early career scientists in Germany.  More information can be found on the yHEP webpage. Meetings of yHEP are held during the annual DPG spring meetings.