Getting backlinks is very important for your website. Here are some places to leave a backlink for free.. You can also put your links in your signitures in certain forums. However make sure you don't leave one liner comments on forums. People do not mind if you have a link, as long as you contribute to their discussions.
Geoland's list of forums
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Another way I have found is to check what backlinks your competitors have and try to get a few of them. This is how I find the other websites that are open to exchanging links..
Also leaving comments on blogs is great. When I check my backlinks, all the forums and blogs I have been to come up. I know they are not the best quality link but they work.
You can also leave comments on this site. There are NO nofollow attributes here!
If anyone else have any more ideas, let us all know..