Links - of interest
Abebooks - secondhand books
Classics archive - (over 400 - mainly Greco-Roman)
Stoics.com - A few interesting ancient texts (Cicero/Seneca/Plutarch) and a few later (e.g. Montaigne) but not the collection of Stoic texts that the site name suggests.
Project Gutenberg - over 40,000 free e-books
Freebooknotes - Useful links to free e-book sites
The Internet Archive - over 8 Million free e-books !