Forum ad slots are auctioned off weekly. Here is the current auction. Here are the ad stats. See the current auction thread for more info.

In addition to the inhouse forum ads, it is common for forum users to sell ad space in their signatures. These ads are not intermediated by bitcointalk.org in any way. If you are interested in advertising in this way, it is recommended that you hire a signature manager.

Main slots (1 in 10 chance)

Nine are auctioned off. One is the factoid slot.

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The World's Betting Exchange

Bet with play money. Win real Bitcoin. 5BTC Prize Fund for World Cup 2018.

Advertised sites are not endorsed by the Bitcoin Forum. They may be unsafe, untrustworthy, or illegal in your jurisdiction. Advertise here.
The World's Betting Exchange

Bet with play money. Win real Bitcoin. 5BTC Prize Fund for World Cup 2018.

Advertised sites are not endorsed by the Bitcoin Forum. They may be unsafe, untrustworthy, or illegal in your jurisdiction. Advertise here.
The World's Betting Exchange

Bet with play money. Win real Bitcoin. 5BTC Prize Fund for World Cup 2018.

Advertised sites are not endorsed by the Bitcoin Forum. They may be unsafe, untrustworthy, or illegal in your jurisdiction. Advertise here.
The World's Betting Exchange

Bet with play money. Win real Bitcoin. 5BTC Prize Fund for World Cup 2018.

Advertised sites are not endorsed by the Bitcoin Forum. They may be unsafe, untrustworthy, or illegal in your jurisdiction. Advertise here.
Advertised sites are not endorsed by the Bitcoin Forum. They may be unsafe, untrustworthy, or illegal in your jurisdiction. Advertise here.
Advertised sites are not endorsed by the Bitcoin Forum. They may be unsafe, untrustworthy, or illegal in your jurisdiction. Advertise here.
Advertised sites are not endorsed by the Bitcoin Forum. They may be unsafe, untrustworthy, or illegal in your jurisdiction. Advertise here.
The World's Betting Exchange

Bet with play money. Win real Bitcoin. 5BTC Prize Fund for World Cup 2018.

Advertised sites are not endorsed by the Bitcoin Forum. They may be unsafe, untrustworthy, or illegal in your jurisdiction. Advertise here.
Factoid (see below)
Advertised sites are not endorsed by the Bitcoin Forum. They may be unsafe, untrustworthy, or illegal in your jurisdiction. Advertise here.

Factoid slots (1 in 640 chance)

Interesting facts, funny quotes, hints, info, and ads given away to supporters.

Sponsored by Private Internet Access, a Bitcoin-accepting .