EUR-Lex is your online gateway to EU law. It provides the official and most comprehensive access to EU legal documents dating back to the beginning of the European Union.

See for example the opinion on the report on Economic and Monetary Union (EMU) in the European Community (Delors report)

DORIE (which stands for DOcumentation et Recherche sur les questions Institutionnelles Européennes) is a database providing access to the collection of documents put together over the years by the unit in the Secretariat-General responsible for institutional issues. The time period covered in DORIE goes from 1946 (oldest document available in the application) until nowadays.

See for example the EU History Album on Jacques DELORS

The Multimedia Centre is the European Parliament’s audio-visual repository provides access to news summaries, live and edited video, infographics, photos or archives.

See for example the topic "Tribute to Jacques Delors"

see ARCHISplus: searching speeches (select speaker "DELORS, Jacques")

In the ECB historical archives you can find documents from the Delors Committee (1988-89) . The ECB historical archives also contain audio-visual material and physical artefacts.

The HAEU preserves and makes accessible for research the archives deposited by EU institutions according to the thirty-year rule governing access to archival material. It also collects and preserves private papers of individuals, movements and international organisations involved in European integration.

The Jacques Delors archives inventory contains “Les dossiers couvrent l’achèvement du mandat de Jacques Delors comme ministre de l’Economie et des Finances sous la Présidence de François Mitterrand, puis les trois mandats exercés comme Président de la Commission européenne entre 1985 et 1994.
The HAEU post Inventory of the Jacques Delors archives available online (17 February 2016) provides a good overview of the archival material in English.