Okay, I have to wait 20 minutes for my bus, so here are a few more ninth chords:

"R" is for root. This is like the "E" form on the open strings.

R-X-X-
---X--
-X---X

This one's like the "A" form on the open strings. The R on the fifth string should be played at some point, either before or after the X on the fifth string, or both, in order to make the harmony clear. Otherwise, it's likely to sound like some other chord, unless you've got a bass player.

XR-X-X
------
-XX-X-


The same applies to this one. It's like the "D" form on the open strings:

--R---
----X-
--XX-X

The same applies to this one, too. The root is quite high, and the X on the fourth string is the fifth, so again, one should make it clear what the harmony is. One way of doing this is to play it on the accented beats, but this is far from a hard-and-fast rule.

--XRX-
-----X
---X--

Here's the one similar to the one discussed above, but with the root on the sixth string:

-X--X-
R-X--X

And that's all seven of the basic forms. With them, one can play ninth chords in every key all over the neck.

I really should proofread this, but I have to get ready to leave.
The characters don't line up well, but they will if a fixed-width font is used. Sorry, no time to find a better solution.