The BYU collection includes Corpus of Contemporary American English, the TIME Corpus of American English, the British National Corpus, the OED, and Corpora in Spanish and Portuguese.
This is a BYU-sponsored archive of a wide variety of copora. May be of use in vocabulary work. Includes a Wikipedia corpus, TIME Magazine, Google Books in American and British English, as well as Spanish.
Tom Cobb's online concordancer has a quick lookup and links to many different academic corpora. Also has links to articles about using concordancers, and a variety of "Text Tools." Outstanding program. --Elizabeth
Like Lextutor, this is an online concordancer. You can search for sentences, and browse various indexed corpus files, or upload your own personal corpus. Includes Chinese, Frnech, and Japanese corpora. Created at the Virtual Language Center.
Laurence Anthony's concordancer is a download for Windows, Mac, or Linus. A Getting Started Video and online help docs can be useful. It appears that you load your own corpus into AntConc to start. (See the BYU collection of corpora.)
A corpus based on transcripts of academic speech events at the U. of Michigan. Includes more informal speech as well, and so is very ueful for academic learners.
R. Stannard's colleague gives us a screencast of how to use COCA. The training video also explains what a corpus is and how to use one, so this has a far wider application than just for CoCA.