Writing about bitcoin. Just by sharung your knowledge, you can earn bitcoin. But with this, it requires a lot of knowledge and expertise about bitcoin and cryptocurrencies. The amount of bitcoin you get depends on how you write.
I do not see any such option on this forum. I guess you may be talking about the services related to bitcoin articles. Some people are offering such services where they are providing content writing services in return of bitcoins. I have not tried this and thus do not have any idea whether there is demand for such service in this forum. However, I have seen such articles being required by clients in different marketplaces.
Signature Campaigns. This is one of the profitable way to earn bitcoin. Bitcointalk forum includes a product campaign in the signature (as what am i doing). Some campaigns have post requirements which you need to obtain to earn. The amount of bitcoin you earn varies on your rank
Signature campaigns are a good opportunity for the members here to make money. I have got accepted in an campaigns and this is my first time.