Not really solar-punk themed as they're a bit too historical but hopefully close enough in theme to be interesting to people here, librivox is great resource and a great example of what can be achieved when people work together.
http://librivox.org/noli-me-tangere-by-jose-rizal/ -- Truly brilliant and beautiful work by the revolutionary hero of the Philippines, largely speaking against the colonialist priests of the catholic church and the inequity of the system imposed on the people; wonderful and rich story with great characterisation and seriously good asides about life, politic and the world.
https://librivox.org/the-ragged-trousered-philanthropists-by-robert-tressell/ -- Written by a jobbing painter, this gritty tale of the life of a working man in Victorian England is powerful both for it's prose and passion, sad as it is inspiring this work is a must read for anyone interesting in the history of labour and working class sentiment.
https://librivox.org/a-dolls-house-by-henrik-ibsen/ - One of Ibsen's many fantastic plays, in this Nora realises she isn't a song bird and dances a tarantella wile delivering some wonderfully powerful lines to a great collection of characters. Also check out Peer Quint it's probably one of the best plays ever written, also it's soundtrack by Grieg is brilliant.
https://librivox.org/hard-times-by-charles-dickens/ -- a classic which shouldn't be overlooked simply for being so popular, if you didn't study it in school then certainly give it a listen, a vital work of English literature from one of the great progressive fathers of English Reform. In it Dickens introduces us to the many hardships, problems and inequities of life in Victorian England.
https://librivox.org/les-miserables-vol-1-by-victor-hugo/ - Brilliant novel, considered one of the 19th centuries best 'Beginning in 1815 and culminating in the 1832 June Rebellion in Paris, the novel follows the lives and interactions of several characters, particularly the struggles of ex-convict Jean Valjean and his experience of redemption.'
https://librivox.org/king-coal-by-upton-sinclair/ -- Sinclair expresses his socialist viewpoints from the perspective of a single protagonist, Hal Warner, caught up in the schemes and plots of the oppressive American capitalist system. The book itself is based on the 1914-1915 Colorado coal strikes.
https://librivox.org/news-from-nowhere-by-william-morris/ - 'News from Nowhere (1890) is a classic work combining utopian socialism and soft science fiction written by the artist, designer and socialist pioneer William Morris.'
https://librivox.org/looking-backward-2000-1887-by-edward-bellamy/ - Fascinating time-travel story about a guy who moves forward to the year two thousand to find a utopia, kinda a disheartening read in 2015...
https://librivox.org/the-woodlanders-by-thomas-hardy-2/ -- [also his other works like Jude the Obscure] A powerful assault on the class structure and sentiment of the day, set in the semi-fictional Wessex it shows how sticking with 'the system' does nobody any favours, it's not a fair or sensible system at all. (this version read by Tadhg is really beautifully read)
https://librivox.org/the-iron-heel-by-jack-london/ - 'A dystopian novel about the terrible oppressions of an American oligarchy at the beginning of the Twentieth Century, and the struggles of a socialist revolutionary movement.'
https://librivox.org/the-jungle-by-upton-sinclair/ - 'Sinclair wrote the novel to portray the harsh conditions and exploited lives of immigrants in the United States in Chicago and similar industrialized cities. However, most readers were more concerned with his exposure of health violations and unsanitary practices in the American meatpacking industry during the early 20th century, based on an investigation he did for a socialist newspaper.'
https://librivox.org/moving-the-mountain-by-charlotte-perkins-gilman/ - 'Moving the Mountain is a feminist utopian novel' 'first volume in Gilman's utopian trilogy; it was followed by the famous Herland (1915) and its sequel, With Her in Ourland (1916)'
Elizabeth Gaskell - https://librivox.org/author/410 - 'Often referred to simply as Mrs Gaskell, was a British novelist and short story writer during the Victorian era. Her novels offer a detailed portrait of the lives of many strata of society, including the very poor, and are of interest to social historians as well as lovers of literature.'
George Bernard Shaw - https://librivox.org/author/603 - 'Irish playwright, essayist, novelist and short story writer. Nearly all his writings address prevailing social problems, but have a vein of comedy which makes their stark themes more palatable.'
Oscar Wilde - https://librivox.org/author/114 - Fantastic and funny playwright and wit of the late nineteenth century, wrote many dramas tackling social issues and class.
https://librivox.org/siddhartha-by-hermann-hesse/ "Siddhartha is one of the great philosophical novels. Profoundly insightful, it is also a beautifully written story that begins as Siddhartha, son of an Indian Brahman, leaves his family and begins a lifelong journey towards Enlightenment. On the way he faces the entire range of human experience and emotion:"