I think signature campaign is may be the best way for people who are starting their new journey in bitcoin because it can helps them a lot to earn bitcoin in a fast way . I also suggest to sell service to other members like offering your programming skills or web designing and get paid on btc.
Signature campaigns are good but i will not consider it a fast way of earning bitcoins,it only provides some extra income which can be treated as a bonus,but yes if we have skills like webdesigning or writing,then we can work as a freelancer and take payment in bitcoins.
Signature campaign is a great reward here in this forum but it doesn't mean we have to focus in that kind of methods since we need to explore more things out to earn bitcoin as signature campaign are not meant to forever.
There are really lots of ways to earn bitcoin and a person can also make a unique way to earn bitcoin out of their beautiful mind.
Yeah there is other ways to earn bitcoin if you are a publisher and you can make a good blog there is some advertising network which paying in bitcoin like a-ads. and usercloud which is paying in bitcoin per download.. also pay per install like perinstallcash they are paying also in bitcoin..