Start with online social networking (i.e. Facebook, Twitter, Blogs etc.). Research topics that relate to your business. Our business is a
Seattle junk removal business, so we research items that relate (recycling, waste management, hauling etc.).
Once I find others who are talking about similar items I try to branch out to them, by directly contacting them about items we hold in common. For instance donation organizations and junk removal companies have a common item, we have donatable goods and they want donatable goods.
We contacted one donation organization about acceptable items via their facebook account and set up a donation drive. Then started collecting clothes and books and will be giving these to them shortly.
This created a connection for us (networking), they in turn liked our facebook page and commented on some of our posts that related. It also created a "snowball" effect of other business contacting or liking our page.
The important thing here is that you make initial contact in the public arena, you find similar ground and follow through with something that is in real life. Easy networking route to follow.
There are actual business networks, but why pay for meeting up with people when you can already do it for free.
Source: http://buzz-bee.net