http://scoobysworkshop.com/2012/07/29/100-places-to-do-pullups/

Pullups are the #1 best way to build wide, flaring lats! Many of you though say that you dont have anywhere to do pull-ups but pull-up bars are everywhere!!!! Dont believe me? Check out this video where in three hours I found 100 places to do pull-ups.

In the home:
doorway mount pullup bars
unfinished attic rafters
basement pipes and rafters
clothes drying racks
garage door opener tracks
tree limbs
In the city:
back side of stairs
back side of bleachers
soccer field goal posts
playgrounds
school playgrounds before or after school hours
from tree limbs
On the farm:
barn rafters
tree limbs
tractor buckets
Use your imagination! What helps a lot is a rope and handle contraption, below are two examples that you can easily make. With these portable pullup bars all you need is a strong overhead beam or tree limb and you can do pullups anywhere. Just toss the rope over and go to town!