lacing “Donate” link or click on a web site can be an effective way to make money, especially if the blog is a niche where readers learn and gain value from content.
Personal development and productivity blogs, for example, are generally well with the donation of systems (one good example of Steve Pavlina).
Minor variations of this method, as some time ago to buy me a beer plugin. This WordPress plugin allows you to add a custom message at the end of each article, we ask readers to chip for beer or coffee.