These are the collected stories of Usagi previously published in Usagi Volume 1 and elsewhere.
Volume 1 of the TPB series consists of books 1-7 and is published by Fantagraphics. (Only the first seven Usagi Yojimbo trades should be indexed here, the Dark Horse collections should be indexed as individual volumes as per indicia.)
Volume 2 of the TPB series can be found under their individual titles or on the volume 2 page. This volume is currently ongoing and continues with Book 8, published by Dark Horse, released in 1996.