/lit/ - Literature

Here are some websites that may provide useful for different vehicles.

https://www.accesstoinsight.org/
This is a website that contains suttas from the Pali Canon, or the Theravadan lineages key texts. It also has study guides and dharma talks from the great sages of the Thai Forest tradition.

http://www.ahandfulofleaves.org/library.html
This is a Buddhist library with free pdf's many of which are very useful for understanding the history and philosophy of Buddhism. Has Theravadan and Mahayana texts.

http://seeingthroughthenet.net/books/
This has Theravadan books and texts that are useful for understanding the lineage.

https://www.dhammatalks.org/
This has many books and dharma talks in the Thai Forest tradition of Ajahn Chah and Bhikku Thanissaro. Great for an introduction to Theravadan thought. Has free physical books for shipping.

Now to Tibetan Mahayana,

https://studybuddhism.com/
This has an introduction to Tibetan Buddhism that is worthwhile to look into.

https://www.lamayeshe.com/
This has free physical books for distribution in the Gelug tradition, as well as books for purchase.

https://www.dawnmountain.org/
This is a sangha that teaches all lineages of Tibetan Mahayana.

Chokyi Nyima Rinpoche
https://dharmasun.org/

Tsoknyi Rinpoche
https://tsoknyirinpoche.org/

Mingyur Rinpoche
https://tergar.org/

14th Dalai Lama
https://www.dalailama.com/

Khenpo Tsewang Dongyal Rinpoche
https://www.padmasambhava.org

Lama Lena
https://lamalenateachings.com/

Alan Wallace
http://www.alanwallace.org/

Tenzin Wangyal Rinpoche
https://ligmincha.org/

James Low
https://www.simplybeing.co.uk/

Jetsunma Tenzin Palmo
http://tenzinpalmo.com/

Dzigar Kongtrul Rinpoche
https://www.mangalashribhuti.org/

Dzongsar Khyentse Rinpoche
https://khyentsefoundation.org/

Khenpo Tsultrim Gyamtso Rinpoche
http://www.ktgrinpoche.org/

Lama Yeshe & Foundation for the Preservation of the Mahayana Tradition
https://fpmt.org/

Thubten Chodron
http://thubtenchodron.org/

Thrangu Rinpoche
http://www.rinpoche.com/

Dzogchen Ponlop Rinpoche
http://www.dpr.info/

17th Karmapa
https://kagyuoffice.org/

Samye Ling monastery
https://www.samyeling.org/

Sakya Trizin
http://hhsakyatrizin.net/

Orgyen Tobgyal Rinpoche
http://all-otr.org/

That is all. Finally we have:
http://www.buddhanet.net/
This has many pdfs and dharma talks on all three Vehicles.

https://dharmaseed.org/
Has many dharma talks on Theravadan and Mahayana traditions, as well as few on Tibetan Mahayana.