I have never tried any of these, but CrystalGraphics has a number of what they call PowerPlugs. These are plug-ins to various Office products. There are PowerPlugs for PowerPoint, FrontPage, Outlook, and Excel. The PowerPlugs can either be purchased as a suite, or individually. I’ll probably ask to review the PowerPlugs for Outlook at some point. There are plug-ins for antispam, music, stationery, emoticons, and more.
From the site:
Microsoft Outlook is great. But, let’s be honest: Its emails are plain vanilla. Energize it with distinctive designer email stationery, music, animated marquee, photos, still and animated emoticons, witty famous quotations and more. CrystalGraphics offers a growing list of exciting ways to personalize your Microsoft Outlook emails!