Really interesting wikipedia article on them too (the article borrows from it a bit).

This is really amusing to me:

> The Michigan Exploration Laboratory (MXL) suspects that the M-Cubed CubeSat, a joint project run by MXL and JPL, became magnetically conjoined to Explorer-1 Prime, a second CubeSat released at the same time, via strong onboard magnets used for passive attitude control, after deploying on October 28, 2011.[5] This is the first non-destructive latching of two satellites.[6]