You can earn the most bitcoins by freelancing. In my opinion its easier to find jobs that way as you are in a nieche that you can manage for yourself.

You can earn bitcoins by doing the advertisement. It basicly come to a signature campaign on this forum, but not only that. You can participate in a lot of others affiliate programs.

If you want to have a fun while earning a bit, and you do not mind the low payment, you can play games like Satoshigalaxy.com - an awesome MMORPG, or a Bitfootball.net - a football manager.