Suspicious Package is a plugin for Quick Look. Quick Look is that feature of Mac OS X 10.5 that allows cover flow views of documents.
In the case of Suspicious Package, you get to preview the contents of a standard Apple installer package without launching the Installer.
Just select the icon in the Finder and select Quick Look to see what will be installed when you double click on the package.
For more information and download, go here: http://www.mothersruin.com/software/SuspiciousPackage/download.html
