Taken from my stickied post in the Hinduism subreddit

Introductory stuff

1. Ramayana(authored by Valmiki) ,paraphrased by Rajagopalachari (pdf)
2. Mahabharata(authored by Vyasa) ,paraphrased by Rajagopalachari (pdf)
3. Of particular importance is What you need to know about Gurus,and all about Gurus (pdf)

Advaita Vedanta

1. An introduction to advaita Vedanta by K Ramakrishna
2. A summary of Adi Sankara's Vedanta commentary compiled by V Swaminathan (pdf)
3. Dakshinamurthy Stotra with a commentary. (pdf)
4. Sadananda Yogindra's Vedanta-sara,with comments by Swami Nikhilananda (pdf)
5. The Bhagavad-Gita,with Adi Sankara's commentary (pdf)
6. The Vedanta-Sutras,with Sankara's commentary (pdf)
7. Sri Madhusudanasaraswati's Vedanta-kalpa-latika (pdf)
8. Hagiography of Adi Sankara,the founder of the school of Advaita Vedanta
9. Biography of Appayya Dikshita,an exponent of Sivadvaita
10. Works of Appayya Dikshita

Dvaita Vedanta

1. Dvaita Vedanta—Madhva's Vaishnava theism by KR Paramahamsa (pdf)
2. Philosophy of Sri Madhvacharya by Dr. BNK Sharma (pdf)
3. Madhva's Bhagavad-gita-bhasya and tatparya-nirnaya translated by Nagesh D Sonde (pdf)

Visistadvaita Vedanta (Sri Vaishnavism)

1. A dialog on Hinduism (pdf)
2. Visistadvaita—A Philosophy of Religion by KR Paramahamsa (pdf)
3. The life of Acharya Ramanuja (pdf)
4. Handbook of Sri Vaishnavism (pdf) by Sri Rama Ramanuja Achari
5. A paraphrase on Acharya Ramanuja's commentary on the Gita (pdf)
6. A translation of Vedantadesikan's Tattvamulakalpam (pdf)
7. Ramanuja's commentary on the Vedanta Sutras -The Sri Bhashya in two volumes: Volume 1 and Volume 2 (pdfs)
8. Yoga from a Vaishnava perspective (pdf)

Achintya Bhedabheda (Gaudiya Vaishnavism)

1. Bhagavad Gita-Its feeling and philosophy (pdf) by Swami BV Triprurari. Another commentary by BV Narayana Maharaja
2. The Fundamentals of Vedanta by Neal Delmonico (where Sadananda Yogindra,and Baladeva Vidyabhusana are presented together).
3. The Vedanta-Sutras of Badarayana with the commentary of Baladeva by Rai Bahadur Srisa Chandra Vasu (This is the Govinda-Bhasya commentary)
4. The Nectar of Instruction (Upadesamrta)- A commentary by Swami BR Sridhara another edition with commentaries by Sri Radharamanadasa Goswami , Sri Bhaktivinoda Thakura and Sri Bhaktisiddhanta Saraswati Thakura (both pdfs)
5. Sri Siksastakam, with commentary of Swami BV Tripurari Maharaja (pdf)
6. A drop from the ocean of the Nectar of Devotion (Bhakti-rasamrta-sindhu-bindu) by Sri Vishwanatha Chakravarti Thakura (pdf)

Shaktism

1. God as Mother by Swami Chidananda
2. Discourses of Sri Chandrashekhara Saraswati on Soundarya Lahari-Part 1 and Part 2 (both pdfs)
3. Devi Gita
4. Devi Bhagavatam
5. Shakti and Shakta by Arthur Avalon
6. The World as power by Arthur Avalon (pdf)
7. Varnamala by Arthur Avalon (pdf)
8. Lalitasahasranama Stotra-an insight by Swami Shantananda Puri
9. Lalitasahasranama stotra with Ashtalakshmi Stotra(an explanation and translation)
10. Saundarya Lahari with meaning
11. Lalita Sahasranama-translation and meaning
12. Devi Mahatmayam translated, Sanskrit verses in IAST script and its significance
13. Amazon list

Kashmir Saivism

1. Kashmir Shaivism-the secret supreme (pdf) by Swami Lakshmanjoo
2. The Doctrine of Vibration (pdf) by Mark Dyczkowsky
3. Shiva Sutras-the supreme awakening (pdf)

Saiva Siddhanta (includes texts of the Nandinatha lineage as well)

1. Facets of Saivism (pdf) by Swami Harshananda
2. Notes on Saiva Siddhanta by Dr. K Ganesalingam
3. A compilation of Saiva Siddhantika texts.
4. Periyapuraanam-lives of the 63 Nayanars by Sekkizar
5. Living with Siva (Himalayan academy,which is from the Nandinatha lineage)
6. Merging with Siva:Hinduism's contemporary metaphysics (Himalayan Academy,which is from the Nandinatha lineage)

Virashaivism (Lingayats) , founded by Basava

1. Introduction
2. Pancha-acharyas (The five 'founder'(for lack of a better words) acharyas of Virashaivism)
3. Akka Mahadevi
4. Series of vachanas