-Perils Of The Young Kingdoms contains five adventures, most of them enjoyable.
-Rogue Mistress is a nice campaign, as it been said before.
-Sailing of the Seas of Fate. Everything on the Oceans of the Young Kingdoms (Ships, weather, travel, sea combat, sea monsters...). The book can be quite useful, given the imporance of sea travel in Elric's world. Contains an adventure on a haunted Menibonean battlebarge.
-Slaves of Fate is a well playable D20 adventure for Dragonlords of Melniboné. There's a conversion for Stormbringer 5 available on Chaosium's site.
-Sorcerers of Pan Tang is problably the best of the lot. Half sourcebook, half adventures, the book focuses on the archvillains of the Young Kingdoms. Even if most the rules (especially sorcery) are now obsolete, the background part and the adventures make the book worth of it. I had a great time torturing my players the Pan Tangian way while running the adventures...
-Unknown East. Less useful than the out of print Atlas of The YK, the book contains nonetheless nice information for players and GMs interested by the Eastern Kingdoms.
Chaosium's Site also has a couple of freely downloadable Stormbringer adventures. Don't miss them.