The people of the Summer Isles have ebony skin (I: 29)
The Summer Isles makes a rare, sweet amber wine (I: 101)
High-masted swan ships with white sails, described as magnificent (I: 142. IV: 508)
The folk of the Summer Isles have princes (I: 247)
The people of the Summer Isles wear fantastic capes made out of colorful feathers (I: 247. II: 315)
The Summer Isles has a golden wood (I: 261)
Women wear feathered gowns (I: 317)
Certain rare spices from the Summer Isles are used in the making of poisons (II: 15)
A white bird from the Summer Isles given as a gift (II: 96)
Feathers from the Summer Isles are sold by Westerosi merchants (II: 127)
The accent that those of the Summer Isles speak with is flowing and liquid (II: 174)
The people of the Summer Isles consider their blood to be that of summer (II: 175)
Tall Trees Town is a place in the Summer Isles (II: 315)
Summer Islanders kiss lightly on the fingers as either a sign of respect or farewell (II: 316)
The Red Flower Vale has a prince (III: 432)
Dancers from the Summer Isles in robes of bright feathers and silk are sometimes hired for special events in Westeros, such as royal weddings (III: 678)
The Summer Isles produce strange, sweet wines. Even in Oldtown, they are very expensive (IV: 6)
Summer Islanders are unafraid to sail out of sight of land (IV: 520)
Barrels of spiced rum (IV: 520)
Swan ships have high forecastles (IV: 520)
Blackbelly rum (IV: 523)
Women serve on swan ships, and can even lead the red archers that help defend the vessel from attack (IV: 523-524)
The double-curved goldenheart bows used by Summer Islanders can send a shaft four hundred yards. Goldenheart is the best wood for making bows, and the Summer Islanders are probably the finest archers in the world (IV: 523. SSM: 1)
Men and women have separate cabins on swan ships (IV: 526)
Menial tasks on a swan ship: scrubbing descks, smoothing descks with stones, hauling anchor chains, coiling rope, hunting rats, sewing sails, patching leaks with hot tar, boning fish and chopping fruit for meals (IV: 526)
Swan ships, as they're called in the Seven Kingdoms for their great white sails and figureheads which are often carved in the shape of birds, are very large and with a good wind behind them can outrun any galley. However, they are helpless when becalmed (IV: 527)