Yesterday, I posted info about using Google to find paying advertisers for your blog.
Here are a few additional strategies you can use:
(1) Visit other blogs and websites in your niche. Who is advertising with them? Again, following my previously suggest strategy (back to Google advertising post), follow the tasks.
(2) Affiliate programs. Some affiliates in your niche will be interested in advertising on your blog. You need to evaluate whether you want to extend an offer to them – sometimes it's in your best interest and other times it will kill your sales. However, don't pass up other interested items your reader desires that are outside your niche. You may sell socks but they also need shoes.
(3) Review classified sections (print and online) and who is advertising there. Check with them as to whether they are interested in advertising on your blog.
Again, you will need to find the previous post with the strategy steps for the rest.