The MacPGP Kit is a set of AppleScripts that talk to any AppleScriptable version of MacPGP. It will give you a small PGP icon in the top right hand corner of your screen (next to the help balloon button), with which you will click on to see a list of available functions to perform. You can encrypt/decrypt/sign the clipboard, add/sign/remove/view keys on your keyring, all at the click of the mouse. It also comes with some very easy to use utilities to make your macintosh more secure in general.
The newest version of the MacPGP Kit (1.7.1) comes with the Eudora->PGP scripts So if you would like both (and most people do), you now only have to use one installer.