“K” is for an awful lot of stuff, so I’ll try and be representative rather than comprehensive.
Kodansha! Where to even start with Kodansha? They used to work with a number of stateside publishers to license their properties, even going so far as to sharing a first-look agreement with in-limbo Del Rey, but then they ended that, yanked their licenses back from Tokyopop, and started a fairly tepid stateside publishing project of their own. They’ve got a panel scheduled at this year’s New York Anime Festival, so maybe they’re ready to kick things off properly. They’ve got a lot of great seinen magazines and properties, though.
Viz is serializing Kingyo Used Books, written and illustrated by Seimu Yoshizaki, on its SigIKKI site. It’s about the power of manga nostalgia. Other SigIKKI contributors include Mohiro Kitoh of Bokurano: Ours fame and Puncho Kondoh of Bob and His Funky Crew “fame.”
Yen Press will publish Kakiffy’s K-On! It’s a four-panel gag manga about a school music club. It originally ran in Houbunsha’s Manga Time Kiara, and I know a few people who really like the anime.
Speaking of four-panel manga published in English by Yen Press, they’ve got two from Satoko Kiyuduki. There’s the excellent Shoulder-a-Coffin Kuro and GA: Geijutsuka Art Design Class. I don’t know anything about GA, as I haven’t read it, as I resent it for being the apparent cause of Kiyuduki suspending work on Shoulder-a-Coffin Kuro.
The Kurosagi Corpse Delivery Service (Dark Horse), written by Eiji Otsuka and illustrated by Housui Yamazaki, originally started in a shônen magazine but currently runs in a seinen publication, Kadokawa Shoten’s Young Ace.
Kujibiki Unbalance (Del Rey) has kind of an odd provenance. It was the manga obsession of the characters in Kio Shimoku’s Genshiken (also Del Rey), and the popularity of Genshiken led Shimoku to collaborate with Keito Koume on an actual version of the fictional comic. It ran in Kodansha’s Afternoon.
Yuji Iwahara’s King of Thorn (Tokyopop) isn’t as good as his Chikyu Misaki (CMX), but he’s an amazing artist. King of Thorn ran in Enterbrain’s Comic Beam.
Kazuo Koike has written one of the most famous manga to be made available in English, Lone Wolf and Cub (Dark Horse), which was drawn by Goseki Kajima. Koike and Kajima also collaborated on Samurai Executioner and Path of the Assassin, both available in English from Dark Horse. Koike collaborated with Kazuo Kamimura on Lady Snowblood (Dark Horse) and Ryoichi Ikegami on Crying Freeman (Dark Horse). Koike also taught a college course in how to be a manga-ka.
Someone really needs to license Fumi Yoshinaga’s Kinô Nani Tabeta? It’s Yoshinaga’s first time writing for a seinen magazine (Kodansha’s Morning), and she’s writing about food again.