The first option we'll be looking at is Chitika (www.chitika.com). Chitika is a very innovative contextual advertising programme because it can serve very detailed advertisements. For example, on your technological gadget blog, Chitika will show advertisements for tech gadgets such as iPods. The way they show it is in different tabs: one for ?Best deals?, another for ?details?, another for ?reviews? and so on. This way, it is more of an informational section for your visitor rather than an advertisement, and naturally the click-through will be higher. You can apply here: https://chitika.com/application.php?type=mm

You can also be an affiliate for Amazon.com. Amazon offers a wide range of products but its predominant domain is in books. Whatever your niche is about, you can probably find a book about it on Amazon.com. Join their Associate programme here: https://associates.amazon.com/gp/flex/associates/apply-login.html/

Once you join them, you can refer visitors to them and earn up to 10% commission. It's not a lot but if you can manage to refer big volumes of visitors, Amazon is for you. This programme really shines when it comes to the ways you can refer visitors: you can use their predefined templates to pull up recent items that match a certain criteria you set, you can target your ad to show a specific item on sale or you can just simply weave your referral links into your blog posts.

Last but definitely not least, you can sell advertising space on your blog if your blog is truly popular. Just take a look at blogs like http://xiaxue.blogspot.com. That blog receives over 10,000 pageviews every day and naturally merchants will want to strike a deal with the blog's owner to post their advertisements there. If you manage to pull in huge amounts of traffic like that blog, you can definitely get people to buy ad space on your blog for prices from $150/month upwards, depending on your blog popularity.
To gauge how much pageviews and visitors you get everyday, just use the free tool available at www.statcounter.com. They have a very detailed setup guide there so I won't go into it.

If your blog has not acquired large amount of visitors yet, you can still sell ad space on your blog on a per click or per impression basis. Just visit sites like www.adbrite.com. For a complete list of these sites, visit http://performancing.com/node/60.

Hopefully, that will help you maximize earnings and profits from your blog!