I am using Blender 2.66 and a newbie I was working on a tutorial which is with the 2.5 version. And I am unable to find the Action editor in version 2.66 while trying to animate a walk cycle. Had it gone? or otherwise can use any other way? Please help. Can the NLA editor do what can be done with the action editor?
The Action Editor is a mode of the Dope Sheet
The Action Editor can be found while in the Dopesheet view ( ShiftF12) as one of its modes.
Can the NLA editor do what can be done with the action editor?
I sense you are thinking of it as an alternative so I say not exactly or plain no.., these are two separate views that serve different purposes though the Action Editor is somewhat of a more detailed view of what you work with in the NLA Editor. The relevant wiki pages offer a more detailed explanation, Action Editor, NLA Editor.