I make $1000 a month now -- and nearly 95% traffic is sent from Google. Not too many visitors though, as I only get about 500 per day. I get around $300 per month in Ad Sense too and it is climbing, so that is a good thing. The adsense pays for my server.
I just won a major keyword phrase in Google that currently lists me as number one. I do not advertise anywhere -- it's all 100% natural marketing. I am still working on getting about 5 other keyword phrases in my niche, and if I am successful, then I will be making about $5000-$8000 per month. It's a very realistic goal for me too, as 95% of my traffic comes directly from that single keyword phrase I am listed for number one in Google.
Referrals won't really help me out because of the niche I am in, so it's up to locking down those other 5 keyword phrases I am targeting. This is also why I am frustrated right now with figuring out how to get the meta and title tags changed for the category pages. If I could do that, then I could double my traffic within about 14 days by getting double listings in Google.
Here's a tip for some of you... I used a service called
Service Wrap and I highly recommend them. It cost me about $159 to use their Gold service plan, but 6 months later, I got number one in google. I won't say what the keyword phrase is, but I will testify that this service works well. Also, the info they give seems shotty on their web site, but I am telling you now, it was the best dang $160 I ever spent for my web site.
Pligg can be very profitable if you have the right niche.