Luminarium
An excellent collection of links to summaries and texts of the great mythological cycles of Ireland, as well as links to works by more modern authors such as James Joyce and Samuel Beckett. Some documents are available in Gaelige.

Rampant Scotland
A library of Scotland's finest. Begins with late medeival works and progresses on through the modern age.

Scottish Radiance
Poetry ancient and modern in Gàidhlig. A good way to study the sounds and rhythms of Scots Gaelic, as there are audio clips to go along with various proverbs and poems.

Medieval Irish Poetry
Sources for medieval poems, analysis of their structures, and instructions for how to write old-style works.