Well isn’t this clever:
The FontShop Plugin Beta allows designers and other type enthusiasts to try out FontShop fonts directly inside Adobe® Photoshop® CS5 and CS5.5. You can preview any of the over 150,000 FontShop fonts for free, in the context of your own artwork.
Fonts are previewed as bitmaps rather than live, editable text. Text layers are auto-hidden while the bitmap versions are shown.
It seems the plug-in doesn’t yet work properly inside the Photoshop CS6 beta, so you might need to choose the CS5 version of Extension Manager to install it inside CS5.
[Via]
It does install with Extension Manager CS6 and seems to work in PhotoShop CS6.