I use PCM Keyboard. Used to use version .14 for a long time, but recently made a skin for .23, so I am using that now.
Here is a recent thread with some .23 skins for anyone who is interested.
http://forum.ppcgeeks.com/showthread.php?t=59446
Of the other keyboards (I have tried many of them), SPB version 4 is good (3 sucked), TouchPal is ok but kind of overrated, the new Diamond 2 keyboard is not bad (looks nice), didn't care for Resco, Zoomboard was a joke, tried shapewriter but was too lazy to figure out how to use it well.