Right, so the only gaiden now is the Kakashi Gaiden which explains how he got the Sharingan. I'm sure there are a lot of storyline/plot continuations that we want to see as a gaiden. How are some of mine:

1) 4th Hokage Gaiden

How he grew up, how he trained under Jiraiya, and more of him, Obito, young Kakashi and Rin.

2) Anko + Orochimaru Gaiden

Why did Orochimaru gave Anko the cursed seal, and was their relationship purely master and pupil?

3) Zabuza and the other 6 mist ninjas Gaiden

Just how did Zabuza got spit up from them and how strong the rest really are.

4) Itachi + Shisui Gaiden

Just curious how he looked like and how efficient Itachi was at killing his best friend.

These are the one's I'd really want to see. Hope there will be more gaidens coming out, preferably along with the weekly chapters.