Caffeine is a small applet designed to disable the screen-saver for your Ubuntu desktop. It's been a staple for me since version 10 or so, and I've developed a significant dependence on this applet, installing it with every new Ubuntu upgrade.
Recently, in a rare-display of hubris, the quantity of which can only be described as Microsoft-worthy, the developer and maintainer of Caffeine, Mr. Rueben Thomas, released version 2.6 that was noteworthy for the fact that the manual controls has been removed from the product.
Despite incredible backlash from the (considerable) community, Mr. Thomas maintained his self-centered decision to remove a fundamental product feature based solely on his personal design preferences.
If you're wanting the "old" Caffeine with the manual toggle on the menu bar, then you have one of two choices at present. You can either install a previous branch, 2.5, or you can install a forked branch, 2.7 (aka Caffeine-Plus), both of which return the icon-toggle to the menu bar.
I've taken the 2.5 route - and to install it is pretty easy. (Thanks to AskUbuntu for the solution!)
First, download the deb version here.
Second, install the dependency packages:
sudo apt-get install gir1.2-gtk-2.0 libsqlite0 python-kaa-base python-kaa-metadata python-sqlite
Last, install the deb package:
sudo dpkg -i caffeine_2.5_all.deb
This process will install version 2.5 and you will see the coffee-cup icon in your menu bar.