Nintendo revealed the Japanese accessories, excluding controllers and the like, for the Wii, and the Japanese pricing. Because I’m so good to you, I ran those prices through the online conversion website and what follows are the descriptions and pricing. The US prices aren’t exact, and European prices (both GBP and euro) are probably the same, maybe costing a few less pounds.

• AC Adapter In other words, the plug. Of course the Wii comes with one, but just in case you accidentally crush it with the 360’s power brick, you can buy another one for 3,000 yen/$25 USD.
• AV Cables Sweet, sweet, 480i red/yellow/white Wii Sports goodness is included in the Wii, but spares can be bought for 1,000 yen/about $8 USD.
• S-Video Cables Slightly better than 480i, you can upgrade for 2,500 yen or $20 USD.
• D-Cable This one will more than likely not be released in other regions than Japan, since it’s one of their alternatives to component cables. It costs 2,500 yen for them, if (very unlikely) we do get it, it’ll cost $20 USD.
• Component Cable These are the 480p cables for the Western market, and cost the same as the S-Video cables and D-Cable.
• 512 MB Memory Card The Wii-branded SD card costs 3,800 yen, or $30 USD. Checking the prices on Circuitcity.com, that’s really not that bad. This is an expansion on the 512 MB flash memory already present on the console.
• Wii LAN Adapter For those who prefer wired connections to using the $40 wi-fi dongle, you can buy this USB LAN adapter…and an extra ethernet cable, if you don’t already have one. It costs 2,800 yen, or $23 USD, and should release in December.

From left to right, top to bottom: AC Adapter, AV Cable, S-Video Cable, Component Cable, Memory Card, LAN Adapter. Not pictured: D-Cable.

Via Nintendo Wii Fanboy.