I think most human beings who have become fed up with their job at some point in their lives have fantasized about just yelling "I quit!" and storming out of the office. Although that might feel good for about 5 minutes, you'll soon find that such an action can do irreparable damage to your career.
Here are some ways to make a graceful exit if you leave your job and why they matter:
Some workplaces, particularly those who handle sensitive information, will walk you out the door upon your resignation. This is a matter of data security more than a comment on your personal stability (unless you're also wearing a straight jacket at the time). However, in most cases, you should give two weeks notice. From what I've read and heard lately, giving notice almost seems like some kind of quaint gesture from the past, shunned by the "movers and shakers" eager to achieve their life plans before the age of 30. But even if you don't feel any loyalty toward the company you're leaving, you should still give notice. After all, future employers will be calling folks at that company looking for a reference for you.
Wrap up loose ends
This doesn't mean to finish every project that is pending when you decide to leave. It means passing on to other employees information they will need to finish what you've started. First of all, you're leaving the company. Even if you hated your job there with white hot intensity, it's not fair to burden the person (most likely a former peer) who has to pick up the pieces. You're not going to punish the company by leaving things in shambles. But your old company could very well punish the lowly worker who wasn't able to put the pieces together after you left.
Also, employers are supposed to only confirm your dates of employment if prospective employer calls. Many, however, will be full of praise for you if you left the company in a good way. But if that prospective employer asks about your work ethic and reliability and the company rep says nothing at all, then it's not too difficult to infer the meaning. Also, IT is not such a large world that people don't talk amongst themselves. Your old boss and your prospective boss might some day be at the same Tech convention together, and your name could come up over cocktails.
Don't use your leaving as a threat
If you've found another job, don't expect your manager to counter with a better offer. He or she may do that, but don't let that be your motivation for talking about leaving.
Write a resignation letter and keep it vague
Although you may be sorely tempted to skewer the management staff in a diatribe, resist the urge. Your illumination of the problems inherent in the company may be completely valid, but they will also most likely be completely ignored. It's nice to think you could bring down a juggernaut of incompetence with a single letter, but nah, that's not gonna happen.