Underdark discusses the Feydark.Also:Future Product: Heroes of the FeywildExcerpts Archive: FeywildExcerpts Archive: Underdark -- the FeydarkDragon 360: Design and Development: FeywildDragon 366: Mithrendain, Citadel of the FeywildDragon 381: Channel Divinity: MeloraDragon 381: Wizards Spells of the FeywildDragon 382: Power Play -- Arcane's Gloaming PathDragon 384: Prince of FrostDragon 384: Winning Races -- Winterkin EladrinDragon 384: Winning Races -- GnomesDragon 384: To Walk on Unseen Paths (Rangers and the Feywild)Dragon 386: Channel Divinity: CorellonDragon 386: Channel Divinity: SehanineDragon 387: Wayfaring BardsDragon 390: Winning Races -- EladrinDragon 390: Winning Races -- GnomesDragon 393: Murkroot Trade MootDragone 393: Hexblades -- The Lady's GiftDragon 394: Corellon's DevotedDragon 395: Sword Guard of AstrazalianDungeon 157: Dark Heart of MithrendainDungeon 166: Throne of the Stone-Skinned King (Scale of Wars Adventure Path)Dungeon 176: FomoriansDungeon 183: Ecology of the ScarecrowDungeon 185: The Bramble Queen
Whew! I think I got most of them. Of course, the random item in the Adventurers' Vault may make reference to some Archifey, and Arcane Power, Primal Power and Players Handbook 3 may also make some references to the Feywild.
Practical Guide to Faeries: no other WotC product has yet provided this much Feywild information. The book contains a map, excellent illustrations, and some very creative details about the Feywild. It also includes some skill challenge ideas, and provides excellent role-playing flavor. Ok, so it's a kid's book, which no full grown gamer would probably ever think to purchase (indeed, it even details a Banshrae palace made out of candy), but it definitely has good bits. A great value for under $10 (including shipping).
If I have to ask the GM for it, then I don't want it.