We surveyed the Away.com office to get you the following "unpretentious" staff picks: Vegas Lounge, kind of divey but gets good music and has a really lively atmosphere (blues mostly, but some jazz); House of Blues in Georgetown, though typically the most expensive; HR-71 -- named after bill that made jazz an American pastime -- has casual vibe with a BYO policy (also good for dancing); Twins Jazz and Bohemian Caverns, both on U St, the latter of which also has a great DJ scene spinning old-school soul in the basement; and Utopia, a restaurant that usually has some good live jazz and stays open late. Hope this helps in your jazz-tastic quest!