I would like to provide a comprehensive list of important books to read, like christian_left did, but my reading is neither so broad nor so organized. I would, however, like to recommend from my recent reading Marcus Rediker's Villains of All Nations: Atlantic Pirates in the Golden Age (Beacon Press, 2004). I will attempt to make a case for its political and cultural relevance.
Rediker describes seamen as a maritime proletariat, and the ships they worked on as the factories of the 18th century world--the machines through which large amounts of capital were accumulated. Turning pirate--or choosing to go 'on the account,' in 18th century terms--was as much a labor action as an attempt to get rich. Of use for us today, I think, is the description of the communal and democratic nature of pirate society. The ship was held to be common property, and important decisions (such as who would be captain) were voted on by the crew. Any wealth generated by the operation of the ship was distributed in shares to the entire crew in accordance with compacts (usually written) agreed upon beforehand by the entire crew.
This form of communal self-organization in opposition to the state and to capital is an important precedent for those seeking to resist the current near-hegemony of free market corporate capitalism. Keeping even the idea of such forms of society alive in an age increasingly dominated by obsequience to hierarchy, profit and blind self-interest helps preserve the hope for viable alternative movements. And, although I tend not to believe in national characters, the figure of the rebel against authority and privilege is vitally important to the American mythos. A political movement that incorporated a revival of purposeful rebelliousness could tap into cultural currents very powerful to American society.
Rediker may have an overly romantic view of pirates and pirate society, but his scholarship seems quite sound. For a more in-depth survey of the world of the 18th century seaman, Rediker's earlier, more scholarly book, Between the Devil and the Deep Blue Sea: Merchant Seaman, Pirates, and the Anglo-American Maritime World, 1700-1750 (Cambridge UP, 1987) is also quite good, though longer and less entertaining.