SwapMenu is no longer being actively maintained. The source is freely available so you can build it for your OS.
SwapMenu is a small Status Item-based Mac OS X application. It runs in the background and places a global item in the menu bar which displays the size of the virtual memory swap files currently in use on your computer. This makes it easy to monitor your use of RAM and identify performance problems related to swapping.
You can add SwapMenu to your login items in order to save the trouble of having to launch it every time you log in.
SwapMenu is written in Objective C for the Cocoa APIs and is distributed under the terms and conditions of the Free Software Foundation's GNU General Public License.