This is a simple effector which works with magnetic ball-and-socket joints.
It holds a standard groove mount hot end.
4 LED's can be mounted on the bottom surface, to light your printer's workspace.  On an LED, the longer lead goes to positive.  If you daisy chain the LED's, you can power the four of them with 12v, without any current limiting resistors.  The way I've added little channels and extra holes, you can run the LED leads from the bottom, up one hole, then through a channel and down another hole where friction will hold it agains the next LED's leads.  Thus, you can wire these LED's without doing any soldering, except for one spot on the bottom.

I use these with my magnetic carriages: https://www.youmagine.com/designs/kossel-plus-magnetic-carriage--2

And magnetic ball joint rod ends:  https://www.youmagine.com/designs/magnetic-ball-joint-rod-ends

Contact haydn.huntley@gmail.com if you need an inexpensive source for the ball studs or magnets. I also precisely build carbon fiber printer arms. (All of the arms in a set match lengths within 50 microns.)  My standard lengths are 215mm (Mini Kossel), 288mm (Kossel XL), 304mm (a little longer), and 360mm (for a 300mm diameter bed).  If you need a custom length, let me know...

2014-08-17:  Updated design to improve the system for securing the hotend to make it hold tighter.  A little bit of tape can be added as a shim to make it tighter still.  Also added gutters to run the LED leads through, and common holes to join them together with, to eliminate all but one of the solder joints (the one on the bottom is still necessary).

2016-02-15:  Here is a link to my newest design (which uses a 60mm LED light ring, holds three fans, and has different versions for E3D and J-Head hotends):  https://www.youmagine.com/designs/magnetic-effector-with-3-fans-and-led-light-ring-for-kossel-plus