Another possibility is, the button on the right, in the 3D view. Don't remember the name, but it will produce some kind of "render" of the viewport with the current settings : i.e. it will give view a wireframe if your model is currently shown as wire.
The last possibility I know of is a script by Babynou, from the french forum BlenderClan : click on the links in first post to get a picture showing the idea. But it looks like his personal website is down, and I don't have a copy of that script by my side. The topic talking about it is here : Forums - Python & Plugins - Script pour rendu solide avec wire - The Blender Clan. I asked him if he still hosts it online, stay tuned for the answer.
Another possibility that hits back my memory, is to draw wireframe on shaded model in viewport, then taking a screenshot. To display wireframe on a shaded model, just go to the "Object" panel (access key : F7), in the "Draw" subpanel, there is a group of buttons titled "Draw extra" : just activate the "Wire" button. Then, just make sure you're in shaded mode for the viewport