For me to get passive income at a moment is only from signature campaign no doubt we need to work on it to earn bitcoins but I am ok with that as its giving me good additional income.
Yes Signature campaign is best oppurtunity to earn the passive income here in this forum. Most of the people making income in the forum from the signature campaign or any other ad campaign only. If we can able to offer services like web development, coin creation and signature creation and all means we can make money.
Signature campaigns ain't passive incomes at all! You have to post messages to gain anything from them. Passive means you don't have to do anything other than collecting the profits. Buying a house and renting it is the best example as a passive income.
Or build a website which don't need any updates/maintenance and let it make money for you, passively.