Language (Dictionaries, Grammar, Linguistics)
OneLook Dictionaries
Almost half a million words indexed in 79 dictionaries, all one one page. Very good.
HyperGrammar
A good resource for grammar and usage.
Literary Texts (Novels, Poems, Plays)
The On-line Books Page
Searchable by author and title. Browsing also available.
ReadPrint.com
Many classic literary works.
Literary Study and Research
Bibliomania
Reference works on literature and language, fiction, non-fiction, poetry. Searchable.