I must disagree with whyn. You can network with complete strangers. When I graduated I moved to a different state to follow my wife who found a job first. I didn't know ANYONE for 4 states in each direction. I sat down, decided what I wanted to do then got a phone book, map, and list of businesses from the chamber of commerce. Then you start calling my friend.
The trick is to create what I like to call a 'forced interview'. It doesn't matter if the company has a listed position. It doesn't matter if you know anyone at the company. Simply call up (and here is the hardest part) get past the secretary.
"Hi, my name is xxxx and I just graduated with a degree in xxxxx from xxxxx. I recently moved to the area and have a strong interest in xxxxxx field. I found through (insert generic compliment)recomendations that your company is a recognized expert in this field and was wandering if there would be anyone available for me to speak with regarding the industry in this area, their experiences, etc. etc."
The secretary at this point just wants you off the phone and as long as you sound professional they will pass you along to whom you desire. The goal should always be to get a manager or someone directly involved in making labor decisions.
When directed to whom you are trying to speak with, ask to see if they would have 15-20 min that you could come in and speak them about their profession, issues facing the industry, education, their experience, etc. It is important that you make it sound like you want to talk about them. Who can't make 20 mins to talk about themselves? The answer (for EVERONE in my experience) is no one. I always was able to come in and sit down with someone.
Getting face time automatically gets you in their mind. When there, ask generic questions. When they mention something that you might have in common focus on that, the more you make it sound like you are the same, the more they will associate themselves with you (that is good). Don't be afraid to mention some of your own accomplishments. Obviously your new grad status will and should come up and this is the perfect opportunity to mention that you are looking for employment. Chances are they won't have anything for your but you can still get invaluable information on people, places, and other businesses that might be looking for people.
On my first 'forced interview' the person I was speaking with mentioned another firm and a person he worked years with (this person eventally hired me). They didn't hire me but the information I got from them landed me a job eventually. I got two offers this way, and neither job was listed.
Hopefully that makes some sense. I sat down with every firm in down but in the end was employed.