i boiled this down to a handy bookmarklet that can do this for the current site:
EDIT: you can use this link to a page hosting the bookmarklet to make it easier to "install".
if you've never used one, just go to the page linked above and drag the only link there to your bookmarks toolbar. installed. click while viewing any site to enter no-js mode...
simple, can be used on mobile devices, and it respects your privacy.
Note: a site can prevent this from working by sending a special HTTP header. This is not supposed to be used to view sites you are not building. If you want to make sure it works, don't send the "X-Frame-Options" header.
Note2: yes, this does link to my site, but because it uses the hash, bookmarklets leave no referrer, the site being framed will not appear in my log. i have no idea what it's being used for, nor can i tell even if i wanted to, which i don't.
feel free to download the simple html shell and serve it on your own to alleviate lingering fears.