Seems like a lot of manufacturers are making longtails this year.

Kona has had the Ute for awhile, but apparently they have an electric-assist option now.

Trek will be releasing the Transfer and Transfer + this fall, again with an electric assist.

And of course, the Surly Big Dummy.   Something interesting is the Stoke Monkey, something that's been around awhile.  More of a homebrew solution, but still pretty neat.  You still have to pedal, but it just boosts the power you are putting down if you are carrying a heavy load (think passenger or 200+ lbs).  

This kid is gonna be a ripper.

Bender on a 29'er.  Never thought I'd see that...(on the left)

stolen from emptybeer.  Surly Big Dummy w/ Bikes at Work trailer.

Possibly...