In November 2009, I posted on the older Basel and Leiden editions of Erasmus’ Opera Omnia.
As I recently found out, most volumes of the vast and ongoing project of the Amsterdam edition are now online as well, in open access, and as PDF with OCR text. The latter is not perfect, but it still facilitates research enormously, of course.
For New Testament scholars, most important are the sixth “ordo”, with Erasmus’ NT texts and annotations (five volumes available, out of six published so far; two more volumes are to be published shortly), and the seventh, with the “paraphrases” (only one volume so far). Also the ninth “ordo”, with Erasmus’ “apologiae” etc. is important for a good impression of his New Testament scholarship.
But why not see for yourself the real critical Latin edition of the Praise of Folly, or of the Dialogue on the correct pronunciation of Latin and Greek? I could go on, but I won’t, this time.
For more information on the ASD edition, readers are referred to the site of the Huygens Institute.
Finally, most volumes of Allen’s edition of Erasmus’ letters are available at the Internet Archive. This is actualy the third “ordo” of Erasmus’ works, not repeated in the Amsterdam edition.