Corpora

Lists of corpora under free licences (public domain, CC-BY-SA, GPL, etc.).

You might also want to use Wikipedia as a corpus, see Tagger_training#Creating_a_corpus.

EuroParl — http://www.statmt.org/europarl/ — EU12 languages up to 44 million words per language

Use this if you want to do English--<something> (funny alignments for non-English pairs)

Use this if you want to do <anything>--<anything>

Southeast European Times — http://xixona.dlsi.ua.es/~fran/setimes/ — English,Turkish,Bulgarian,Macedonian,Serbo-Croatian,Albanian,Greek,Romanian — 9,000 approx. paragraph aligned, 90,000—120,000 words.
South African Government Services — http://xixona.dlsi.ua.es/~fran/services-gov-za-en_ZA-af_ZA.txt — English—Afrikaans — 2,500 approx. sentence aligned, 49,375 words.
IJS-ELAN — http://nl.ijs.si/elan/ — English-Slovenian
OPUS — http://urd.let.rug.nl/tiedeman/OPUS/index.php — Open Source multilingual corpora
Open-Tran — http://www.open-tran.eu — single point of access to translations of open-source software in many languages (downloadable as SQLite databases)

Corpus tools

Corpus Catcher — http://translate.sourceforge.net/wiki/corpuscatcher/index - Bootstrap corpora from the web
BootCaT — http://sslmit.unibo.it/~baroni/bootcat.html - Simple Utilities to Bootstrap Corpora and Terms from the Web
Bitextor — http://sourceforge.net/projects/bitextor/ - Bootstrap bilingual corpora from the web