Ragnarok sells a package of several uncial and decorative fonts based on Celtic manuscript hands and decorative knot and spiral fonts. Both Macintosh and Windows are supported.
P22 sells a package of several uncial style fonts based on the Book of Kells and similar manuscripts, and fonts for making Celtic style borders and decorations. Both Macintosh and Windows are supported.
Essentially a Roman alphabet, Gaeilge is a TrueType font with extra characters and diacritics for use with Gaelic. It is the type face used in books printed in Ireland until just a few years ago; there are some minor differences between it and the normal Roman or English alphabet. This font was made by father Padraig McCarthy.
Vintage Type sells Vintage Celtia(TM), a family of fonts with spirals, keys, and knotwork. The fonts are available as both postscript and TrueType for Macintosh and Windows.
Howard Berlin offers Windows Ogham and Gaelige, and other medieval style faces for Windows. This is a good site for non-Latin and international Windows typefaces in general.
A nicely organized and displayed page with commercial, free and shareware fonts. There are several medieval and Celtic fonts here; browse a bit in the Artsy and Script categories.
