Augustinus.it provides the complete works of St Augustine in Latin and Italian. They are organised according the Augustine volumes in Patrologia Latina (PL 32-46). For some reason PL 46 is not included in the "elenchus" on the left but the sermons in that volume can be found by searching "PL 46" in the Tavola Cronologica. Unfortunately it does not include the prefatory material found in the printed volumes. This means it is no help in deciphering the PDF of this discussion of the text of sermones inediti.
There is also a page of links to English translations of his works. Apart from those listed there, I don't know of any others.
New Advent only has a translation of the Summa Theologica, done by the Fathers of the English Dominican Province in 1920. The Dominican House of Studies in Washington, D.C. offers the complete works of Aquinas in more recent translations. (Bookmark that link because there is no obvious way to navigate there from the homepage). It was novices at the DHS who produced that charming work Lives of the Dominican Saints. I wouldn't mention that, except that it always makes Dominicans squirm when I do.