The Grand Exchange

Varrock's trading plaza, walked like your house. Get there from the exit portal in your garden (its Grand Exchange row) and back with the House button or H.

Offers with the clerks

The clerks take buy and sell offers for anything worth something that isn't a unique: buy at about 105% of an item's value, sell at about 95%. Coins (or the items) are taken when you place an offer; it fills over real time, even while you're away, straight into your bank, and you can abort what's left. Up to 8 offers at once. This is where to get anything you can't make yet, like nails, planks or runes.

Merchants

Each specialist buys and sells their trade. Prices move with their stock: buying pushes a price up, selling brings it down, and stock drifts back over time.

Grand Exchange Clerk

Trades in anything you've got. Buys anything at 40% of its value.

Hofuthand

Trades in weapons and armour.

Farid Morrisane

Trades in ores and bars.

Relobo Blinyo

Trades in logs and planks.

Bob Barter

Trades in herbs and potions.

Murky Matt

Trades in runes and essence.

The black market

A shady stranger offers 4 rare items at 4 times their value, a new selection every 6 hours (or pay 5,000 coins to reshuffle). What you buy goes to your bank, not your collection log.