Thanks to Keith Furman for the tip: We broke the story last week about the Windows 98 Easter Egg and now we've got the Easter Egg for Plus!98 as well!
To view the Plus!98 Easter Egg, simply open the Deluxe CD Player and choose Playlist from the menu that appears when you click the Options button (make sure there is a music CD in the drive first). Then, expand the playlist for the CD that is in the drive, choose any song and click the Edit Playlist button. Type "Microsoft Plus!98 Product Team" (no quotes) as the name of the artist and "Credits" as the name of the song title. Hold down the Ctrl key and click Cancel. Now, a new group will appear in the Album Information list box called "Microsoft Plus!98 Product Team." Expand the group to see the various Plus!98 teams at Microsoft and the people that worked on the product.
This change isn't permanent. Once you close the dialog box, the new entry is deleted, so you'll have to repeat these steps if you want to see it again