My opinion on original texts:
A great introduction to the stoics are Pierre Hadot's Philosophy as a Way of Life (his other books are also great), especially the essays:
But also the essay "Marcus Aurelius".
A similar but different angle are the essays by James Stockdale (https://en.wikipedia.org/wiki/James_Stockdale):
Also:
In "Moral Essays volume 2".
Online version: http://www.stoics.com/seneca_essays_book_2.html
On the same site (http://www.stoics.com/books.html) there are versions of:
I recommend the translation by John Davie (Oxford World's Classics)
Online Books by Epictetus http://onlinebooks.library.upenn.edu/webbin/book/lookupname?key=Epictetus
---Discourses---
Online version: http://classics.mit.edu/Epictetus/discourses.html
Discourses and Selected Writings (Penguin Classics), new translation by Robert Dobbin, includes Enchiridion and "fragments" (amazon.com).
---Enchiridion (Handbook or Manual)---
Online versions:
Alternative version of the same text: Enchiridion
(The so-called “Golden Sayings” is a later compendium of aphorisms drawn from the Discourses and Encheiridion.)
A modern rewrite of the manual: http://www.ideonautics.com/manual2.htm
I recommend the translation by Robert Dobbin, although it does not have all the entries of the Discourses.
Alternatively, Robin Hards translation, based on Elizabeth Carter's translation of 1758.
Meditations
Online version: http://classics.mit.edu/Antoninus/meditations.html
The Emperor's Handbook, by C. Scott Hicks and David V. Hicks (newer, dumbed down?)
FARQUHARSON, A. S. L., The Meditations of the Emperor Marcus Antoninus, Edited with Translation and Commentary, 2 vols (Oxford: Clarendon Press, 1944) – arguably the definitive edition and essential for any serious study of the Meditations.
FARQUHARSON, A. S. L.,The Meditations of Marcus Aurelius Antoninus, With Introduction and Notes by R. B. Rutherford (Oxford: Oxford University Press, 1989) – an edition reprinting only the translation from Farquharson’s 1944 edition, but supplemented with a helpful introduction and a selection from the correspondence with Fronto.
Robin Hard ("Eloquent and accurate translation by Robin Hard based on the latest Greek edition.") http://www.oup.com/us/catalog/general/subject/Philosophy/?view=usa&ci=9780199573202
Hard versus Farquharson: http://bmcr.brynmawr.edu/1998/98.6.23.html
Hay is a new translation (and recommended by Ryan Holiday (http://fourhourworkweek.com/2009/04/13/stoicism-101-a-practical-guide-for-entrepreneurs/)):
Meditations [Paperback] Marcus Aurelius (Author) Gregory Hays's new translation Publisher: Phoenix (5 July 2012) Language: English ISBN-10: 0753820161
The Stoics 2nd ed. F. H. Sandbach Published 1898 by Bristol Press in London . http://openlibrary.org/books/OL24151317M/The_Stoics
The stoic philosophy By Murray, Gilbert http://openlibrary.org/works/OL1243262W/The_stoic_philosophy http://www.archive.org/download/stoiephilosophy00murrgoog/stoiephilosophy00murrgoog.epub