Buddhism

Dhamma in a nutshell

Dukkha: There is stress, dissatisfaction, suffering in this world
Samudaya: The cause of dukkha is tanha (thirst, craving, desire), conditioned by avijja (ignorance)
Nirodha: There is an end to dukkha by letting go of tanha and overcoming avijja
Magga: The way to the end of dukkha is the eightfold noble path

Dhammapada (Buddha) – an ancient collection of proverbs, adages, and general reflections on the nature of life and its ills from a Buddhist perspective.
In the Buddha's Words (Bhikkhu Bodhi) – an excellent overview of Buddhist scripture by a popular monk, fairly contemporary
Word of the Buddha (Brahm/Bodhi/Nyanatiloka) – a hypercondensed version of the Sutta Pitaka (download here
What the Buddha Taught (Walpola Rahula) – another overview of Buddhist thought by a contemporary monk
The Buddha's Lists (David Snyder) – Theravada scripture boiled into lists.

Right Mindfulness (Thanissaro Bhikkhu) – a good intro to Buddhist meditation
Right Concentration (Leigh Brasington) – another good intro to Buddhist meditation
The Mind Illuminated (John Yates) – A course on meditation that's well-suited for modern audiences, less based on traditional practice and scriptures.