The guys at my work have been debating this for some time.  Whats your input...
Under boob or side boob?

Yes!

Under boob.  Always gives a rise to my Levis.

I vote UNDER BOOB!!!

I don't think there is a wrong answer.  Just about every set of bewbs has sometning that makes them special.  Some look good from the side, some look good straight on, some look good from the top, some look good from the bottom.  Its important to get a view of them from all angles.  At least thats what I try to do.

Big or small I love them all, but there is something special about a peek from the side.

I agree! I love a side view especially if they hang a little.

"I love boobies..." that's a Charlie Waffles song

I like boobies in general! I don't want to have to decide.

As a guy who likes a little left to the imagination it all depends on the girl who owns the view.  If the niples hang low give me a side view, if them boobies sway wide with nipples on the side give me the bottom view!  Most of all I'll take a cleavage view and a smile or wink!

I think "accidental" is sexier so because of this I choose side boob.  Underboob is nice but it is also blatantly purposeful.

Actually I like completely bare best!

...she is aware and it is a choice she makes and a risk she takes. Men's eyes are instinctively drawn to a woman's breasts and we take any chance we can to glimpse bare skin. We can't help it, we can't stop it and women know this.  
I think my vote goes for side boobs although sometimes, when sideboobs and underboobs are displayed together it can be more than we mere mortal men can handle!

Vorlon, great answer.
What about the "no boob"? Dare I say like some posters in this MN forum..not necessarily on this thread lol.