Conversational English corpus for download

There are many spoken English corpora available. But generally, you need to ask more questions than 'plain text' before you find the right one. Length, level of annotation, format of annotation, type of conversation, genre/register, dialect, natural vs. elicited, etc. Those will all depend on the type of research questions you want to answer.

If you just want any one corpus you could try:

• Santa Barbara Corpus of Spoken American English: http://www.linguistics.ucsb.edu/research/santa-barbara-corpus#Contents

• CHILDES collection of corpora (most is conversation) - http://childes.psy.cmu.edu/

• BASE - British Academic Spoken English http://www2.warwick.ac.uk/fac/soc/al/research/collect/base/

There are others (like the Switchboard corpus) which you can download for a fee or buy on CD (like the Edinburgh Map Task corpus).