The site http://www.euclides.org/ in Catalan has
links for Euclid and the Elements. It includes a translation into Catalan of
the statments of the definitions, postulates, and axioms of the Elements.
The text of Heath's translation of Euclid’s Elements on-line at
the Perseus Project,
http://www.perseus.tufts.edu/, at Tuft's University. Not just Heath's
translation, but his commentary as well as the Greek text is available
at the Perseus Project.
Green Lion Press has published Heath’s version of Euclid’s Elements in one volume.
In 1847 Oliver Byrne designed a wonderful version of the first six books of the Elements with an imaginative use of color to illustrate geometry. Bill Casselman has made this available at http://www.math.ubc.ca/people/faculty/cass/Euclid/byrne.html, at the University of British Columbia.
Richard Fitzpatrick’s Euclid’s Elements of Geometry, 2007–2008, at
http://farside.ph.utexas.edu/euclid/elements.pdf includes Heiberg’s Greek text alongside Fitzpatrick’s translation. It’s in a downloadable and printable PDF format.