Hmm gosh this is a hard one. When Google AdSense first started & studiowhiz.com was a community site (not a blog like it is now) I used to make about $120 US a month - now, I'm just blogging, most of my traffic is StumbleUpon - adsense has made me a few bucks lately ($3 or $4).
If your site is niche eg: www.italkmagazine.com which I used to run (it's up for sale btw) I built up some great relationships with iPhone related suppliers and I had cases, goodies, books, etc to review and give away.
One thing I learned very early on is this: Just Ask - the worst they can say is No. If you want something then ask for it. If they don't say NO then you are wining. If they do say NO, well you've lost nothing.
You will need to have decent traffic levels - but if you do then hit up sites for contact details. Eg: most book publishers have a PR or MEDIA contact who you can talk to. They will want to know your target, niche, size, demographics etc. You have to think like "What's in it for them"
You'll find that companies (esp at the moment) are more willing to part with GOODS than CASH. So, leverage that, start a reviews section and review different types of Dog Food, Cat Food, Car Repairs, Supermarkets - what ever is in your niche. start with the things you have at home already, then go after some companies. They'll look at your site, your writing style etc
Don't get hung up on cash - look for other opportunities. Eg: your host, do they do an affiliate program? If you can get 2 or 3 people to sign up to your host, that might cover your years hosting cost. What about other "trade" type senarios?
(hmm maybe I should write some more indepth blog posts like this ey?)