One of my new ventures is a site that will be Stack Overflow for predictions. Hopefully it will be a high traffic site with many inbound links and targeted keywords.
Assume all the risks bear out and there are many inbound links and a lot of traffic, and I use some reputable ad provider.
How much traffic would it take to generate $1000 per month in advertising revenue?
For a tech blog/website, then $1 CPM (that is, $1 for every thousand hits) is the kind of level I've personally seen, and I get the impression that's not atypical. So, for $1,000/month in revenue I would need 1,000,000 hits. But obviously if your market is such that people are willing to pay more for clicks then you'll get more, and if they're willing to pay less then you'll get less.
(Aside: it's worth noting that I get a better rate from advertisers I've made a direct relationship with than I do from Google AdWords, by a factor of 3 or 4.)
In your comment you say that your site's content is about is "politics, consumer products and stocks/financial events" -- this suggests to me that it's a broader market than a tech blog, which I suspect (but don't know) would mean that your CPM would be lower, so you'd need more than 1M hits to reach your target. In general, as I understand it, the more targeted you are, the higher the rates.