"In versions of Adobe Illustrator prior to 7.0, a Pantone color can be accessed by typing the Pantone number (after importing the Pantone color library and activating custom colors in the Paint Style palette). The new version appears to lack this capability, but there is an undocumented way to activate it. After opening the desired Pantone library off the Swatch Libraries menu selection, click on any color inside the Pantone palette with the Apple and Option keys depressed - the entire palette is bounded after clicking by a thick black border. You can then type the Pantone number to get to the desired number."
Update: Jeremy Hooper points out that this is documented on the back page of the Quick Tips card for the the swatches pallette: "j option-cmd click in the list then press letter keys to select swatch by name."