Online corpora collections
German corpus archive, searchable as COSMAS (1.900.000.000 words !!!)
Very large collection of Portuguese corpora (by Diana Santos, Linguateca), much of it PALAVRAS-annotated (Eckhard Bick)
Corpus del Espanol:
Fast and unabridged comparative corpus of historical and modern Spanish (by Mark Davies)
BNC's Corpus Page:
Overview of English corpora, online acces to the BNC (100 million words)
Mixed British/American English corpus (50 million words), includeds transcribed speech (by Collins)
Internet corpus tools
Searching the internet as a corpus, slow but nice. Keeps going.
Concordancing with the whole internet as a corpus. Fast AND nice.
Other corpora link overviews
Link collection of corpora in many languages at the University of Tübingen (maintained by Laura Kallmeyer)
Link collection of corpora in many languages (maintained by Michael Barlow)
Statistical NLP and computational corpus linguistics:
Link collection of corpora and NLP-resources in many languages at the Stanford InfoLab (maintained by Christopher Manning)