I wrote this little bookmarklet to help me instantly grab the large/original version of any Flickr photo. Funnily enough, because of Flickr's consistent filenaming scheme, it also works for photos where the See different sizes option normally remains hidden:

view big (gets 1024px version; should work for most photos)

view original (gets full version as uploaded; works for photos pre-March 2007)

Drag the link above to your Bookmarks Toolbar (or right click, Add to Favorites), then click it when viewing a single Flickr photo page.

Here's the formatted source code, if you're into that sorta thing:

for (m in M=document.getElementsByTagName('img'))
{
  s = M[m].src;
  if (s && s.match(/static/) && !s.match(/_s|buddy/))
  {
    void(window.open(s.replace('.jpg','_o.jpg'),'_self'));
    break;
  }
}