you have 2 options
1) you resign nicely, i have found a positon else where, i loved working here, thanks for making me part of your team im sorry to go blah blah
2) burn your bridge, light the mother f'ers up and tell them off
theres no soft shoe approach like, im leaving because of a poor work environemnt, if your going to say that just tell them this place sucks dockey balls and piss on the bosses hat.
www.i-resign.com has some good ones. I used the "better postion" else where one.
You don't want to burn your bridge, one never knows...