Free audio readings of the Quran can be listened to or downloaded from QuranEnglish.com. There are four different versions available on that site in MP3 format, as of 2015.
The four recitations are done by Syed Abu Alala Moududi, Abdul Basit, Abdul Waheed Qasmi and Imam Al Sudais, respectively. Each option is composed of around 100 to 160 audio files. Each file contains a Surah of the Quran, with each verse in the Surah recited in Arabic then read in English. Some Surahs are split into multiple files because of length.
You can listen on the site or download files for offline use. The file size of an entire recitation of the Quran with English translation from this site ranges from 682 megabytes to 3.98 gigabytes.