• Socrates (Apology by Plato, a Word document, 130 KB)
• Magna Carta, 1225 (Word, 62KB)
• John Locke,  1690 (Treatise on Govt. Word, 380KB)
• Voltaire  1778 (Letter on Locke, Word, 41KB)
• Adam Smith 1776 (Wealth of Nations, Word 2.6 MB)
• David Hume (390KB, Word doc)
• Edmund Burke 1790 (Reflections on the Revolution in   France, Text file, 570KB)
• James Madison, 1789. Amendments to US Constitution, Word 66KB)
• T Jefferson
• John Stuart Mill, 1859 (On Liberty, Word 311 KB)
• Ayn Rand
• FA Hayek (Use of knowledge in Society,1945, PDF 1.36MB). Do read The Fatal Conceit and The Constitution of Liberty.
• Milton Friedman (Capitalism and Freedom; link to his Indian writings, 1955)
• Peter Bauer
• Buchanan (Soul of liberalism, 2000. PDF 48KB)

List of economists here 

Commentary on Milton Friedman's work.

A review of Constitution of Liberty by Sinclair Davidson