If you have a quality blog you can often earn good money from it. That means earn money while enjoying to write blog.
By quality blog, i meant that your blog has a good number of readers and it has 3+ or 4+ google pagerank (homepage). There are ample opportunities to earn using your blog.
To name a few you can register with www.reviewme.com and www.payperpost.com. You can earn from $5 to $20 for you review/post you write in you blog about the advertiser. You will earn great money if you are from USA, Canada, UK, Australia etc. It can be $25-$500 from these locations. But still offers are available for all other countries too. One of the primary condition is that blog language must be English.
But I have seen that a good number of advertisers frequently disregard blogs hosted in WordPress.com and Blogger.com. So its best that you host you own blog.
To gain more info you should visit the above sites.