Marichi: he is son of Brahma and also come in Saptarishis.

Angiras: he is mentioned in all the Hindu’s Vedas, and supposed to give his major contribution in the 4^th Veda, the Atharvaveda.

Atri: he comes in Prajapatis, and also called the son of Brahma.

Yajnavalkya: he is popular in Upanishads, and gave his major contribution in Brihadrankya Upanishad.

Pulatsya: he comes in Prajapatis as well as in Saptarishis, and is father of Maharshi Agastya and Maharshi Vsravas.

Vashishtha: one of the Saptarishis and Rajguru of Solar Dynasty.

Jamadagni: one of the Saptarishis and descendant of Bhrigu.

Bharadwaj: descendent of Angiras, one of the Saptarishis, and father of Dronacharya.

Bhrigu: author of Bhrigu Samhita, and one of the Saptarishis and Prajapatis.

Agastya: he gave major contribution in Rig Veda’s mantras.

Dattatreya: the Adi-Guru of Adinath Sampradaya.

Ashtavakra: author of famous Ashtavakra Gita.

Vyasa: author of great Hindu epic Mahabharata.

Comparatively new, Nisargadatta Maharaj and Maharshi Raman have been outstanding Advaita Guru. Current stream of advaita is flowing from Poonjaji to Mooji, and Gangaji etc. Though, there are plenty of Advaita Gurus and Teachers … but teachings are more or less is the same, as Nisargadatta Maharaj and Maharashi Raman used to have.

If you are looking for Advaita books, please look for Ashtavakra Gita and Upanishads. Books of Nisargadatta Maharaj and Maharshi Raman are also outstanding.