Delhi City Archives Still in planning stages. The archives in Delhi include millions of documents such as "CID records, Gazettes, maps, manuscripts, photographs, negatives and records of eminent personalities."
Digital Library of India is going through some major changes and can be very slow but if one is persistent, one can find a lot. In any case Author Authority files for Indic names are not very robust. It is therefore critical to try all variant spellings when searching. A shadow copy of the holdings of the Digital Library of India can be found at Archive.org.
Gandhi Heritage Portal. Complete works scanned and digitized. Indexing not complete. Full text search limited.
IndCat. Online union catalog of Indian universities. INFLIBNET Centre, Ahmedabad, Gujarat, INDIA.
Mukul Dey Archives. Mukul Dey (1895-1989) was a Bengali artist in the Tagore circle. His private archive which includes works of folk art and works of fellow "Neo-Bengal School" artists as well as his own drypoint etchings is being organized and digitized. Some items are already available online. You would browse these items by using the "Browse by" list on the right hand side of website. More items are available to scholars who visit the archives in Santiniketan in person. Details are given on their FAQ page here.