⇄ You can buy and sell Namecoins here:

Decentralized exchanges
Bisq

Gold level exchanges
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Silver level exchanges
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Bronze level exchanges
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Basic level exchanges
24change
AltCoinTrader
Bleutrade
bx.in.th
Cryptopia
Livecoin
Poloniex
ShapeShift
Tux Exchange
Vircurexuse with caution, see discussion
WEX

Gold, silver and bronze level exchanges donate to the Namecoin project. The higher the donation the higher the level. Note that the exchanges are not verified in any way. The current fees are 1000/300/100NMC per year. To get on the list contact exchanges a|t namecoin.org