Mentoring

The Mentoring system in EverQuest II allows players to group with lower-level characters. In effect, it is sanctioned power-leveling.

In early July 2008 there is supposed to be a summer-long increase to the mentoring bonus experience.

When you right click a lower level group member, you will see an option to Mentor them.
Selecting "Mentor" will make you appear and perform as if you were the same level as your Apprentice. It will be as if you were that level with a full bar of XP, and had all of the abilities that a person with a full experience bar of that level would have.
The Apprentice will receive an experience bonus while under the guidance of a Mentor. Up to 5 other players can act as a Mentor for a single player at the same time. Each subsequent person Mentoring an Apprentice adds to the bonus experience that the Apprentice receives. A single Apprentice can be mentored by up to five other people.
The Mentors and Apprentice will receive experience, loot, and quest credit as if the Mentor were the same level as the Apprentice.
Mentors do receive viable amounts of experience and advance toward their actual level while mentoring, though at a slightly reduced rate.
A Mentor can right click their Apprentice and select "Stop Mentoring" when they wish to stop acting as a Mentor.
If the Mentor or Apprentice leaves the group, the Mentor will go back to their original level.

Allakhazam credits this post by Gnobrin at the SOE Official Forums for some of the info in this article.