Three volumes of Coke's writings, with translations, notes, commentary, and an introduction, have been published as The Selected Writings of Sir Edward Coke, edited by Steve Sheppard (ISBN 0-86597-316-4). They are available individually as PDF files: vol 1 (pp. 1–520), vol 2 (pp. 521–1184), vol 3 (pp. 1185–1468). These also contain “The First Part of the Institutes of the Lawes of England: Or A Commentary upon Littleton, Not the name of the Author only, but of the Law it selfe”.
Selected Works of Edward Coke at the Liberty Library of Constitutional Classics, Commentary on English common and statutory law, including the Institutes and the Reports.
All four institutes are available from Google Books: First Part (Volume 1 of 1832 ed.)  (1853 American ed. in 2 vols) Second Part (1797 ed.) Third Part (1669 ed.)  (1797 ed.) Fourth Part (1671 ed.)  (1797 ed.)