That is a type of crane fly (a type of fly - order Diptera - in the family Tipulidae). http://bugguide.net/node/view/183
They look alot like mosquitoes - GIANT mosquitoes - but have very different habits. The young develop in mud/moist soil and feed on decaying plant matter. The adults of some species may drink water, but others do not feed at all. And none of them bite. They are very innocuous and not at all harmful to humans.
Crane flies are one of the largest families of insects on the planet. One person (C.P. Alexander) alone identified over 15,000 different species.