Very little has survived from the Stoa. Collections of texts include

Stoicorum Veterum Fragmenta [SVF]

• Stoicorum Veterum Fragmenta, vol. 1: Zeno et Zenonis discipuli
  ed. A von Arnim, 1905 (15 MB)
• Stoicorum Veterum Fragmenta, vol. 2: Chrysippi fragmenta logica et physica
  ed. A von Arnim, 1903 (29 MB)
• Stoicorum Veterum Fragmenta, vol. 3: Chrysippi fragmenta moralia; fragmenta successorum Chrysippi
  ed. A von Arnim, 1903 (21 MB)
• Stoicorum Veterum Fragmenta, vol. 4: Quo indices continentur
  ed. M Adler, 1924 (28 MB)

Fragmentsammlungen are nice and immenseful helpful. Yet to do serious work one has to confront the original texts themselves. A few of the more indispensable ones will be gathered below.

Commentaria in Aristotelem Graeca [CAG]

Between 1883 and 1909 the Berlin Academy edited some 15,000 pages of commentaries on Aristotle in Greek, dating from the second to the thirteenth century ad. In many cases, these editions are still the best we have. They are being translated in the Ancient Commentators on Aristotle Project, under the editorship of Richard Sorabji.—To begin with, the Commentator:

• Alexandri in Aristotelis Metaphysica commentaria
  CAG 1, ed. M Hayduck, 1891 (48 MB)
• Alexandri in Aristotelis Analyticorum priorum I librum commentarium
  CAG 2.1, ed. M Wallies, 1883 (23 MB)
• Alexandri in Aristotelis Topicorum libros octo commentaria
  CAG 2.2, ed. M Wallies, 1891 (39 MB)
• Alexandri quod fertur in Aristotelis Sophisticos Elenchos commentarium
  CAG 2.3, ed. M Wallies, 1898 (13 MB)
• Alexandri in librum de sensu commentarium
  CAG 3.1, ed. P Wendland, 1901 (11 MB)
• Alexandri in Aristotelis Meteorologicorum libros commentaria
  CAG 3.2, ed. M Hayduck, 1899 (13 MB)