Because today (January 5th) is the official release date of the first speed-up volumes, I guess I'll start things off:
One Piece Speed-Up Part 1: Journey to the Island in the Sky!
Volume 24: People's Dreams
Original Japanese Release Date: July 4, 2002
As the Straw Hats leave Vivi and Alabasta behind, they discover a stowaway on board who wants to become a crew meraber! But can they trust this former Baroque Works agent?! Whether friend or foe, they'll be needing all the help they can get when their Log Pose suddenly points to the sky!
Volume 25: The 100 Million Berry Man
Original Japanese Release Date: Septeraber 4, 2002
Talk about impossible! Luffy and the Straw Hats have to find a way to sail to an island in the sky, and the only one who can show them the way is known to be a greater liar than Usopp! It won't be easy, but can they trust their lives to someone nobody believes in?!
Volume 26: Adventure On Kami's Island
Original Japanese Release Date: Deceraber 4, 2002
The Straw Hats have made it to the ocean in the sky, but not everything is as angelic as they had imagined. Charged with illegal entry, they are being pursued by not only the Skypiea Police, but all the other inhabitants of the sky too! Everyone wants them out, but will these outlaws be allowed to leave in peace?!
Volume 27: Overture
Original Japanese Release Date: February 4, 2003
The Straw Hats have been branded criminals for entering Skypiea without paying the toll! Their only chance for a way out is a series of challenges given to them by Kami's vassals. Meanwhile, Nico Robin makes an important discovery about the island. Is there a city of gold hidden on Skypiea?
Volume 28: Wyper the Berserker
Original Japanese Release Date: May 1, 2003
Luffy and the crew are on the move to find the hidden gold in Upper Yard but end up getting caught in the middle of a war between Eneru, who controls Upper Yard, and the Shandia, who seek the return of their homeland. Can the Straw Hats find the gold and figure out an escape route before their three hours are up?