Started in 1864 the Corpus Scriptorum Ecclesiasticorum Latinorum (CSEL) is an academic series that publishes critical editions of Latin works by late antique Christian authors from the late 2nd century until the beginning of the 7th century. These editions are prepared in cooperation with internationally renowned experts according to modern editorial techniques and are meant to serve as a textual basis for scholarly disciplines dealing with late antiquity and replace about a third of Migne; and they mostly have useful introductions.
Many of the volumes can be accessed online at a number of sites, e.g. at Csel-dev by OpenGreekAndLatin
For a list of volumes see: