My favorite frugal entertainment activity is Trivia Night at our local pub. $2 will buy your way in to participating in the trivia event, in which teams of up to 8 people battle it out to be crowned "King/Queen with the most useless knowledge". I am a connoisseur of all things pop culture related, and thanks to wikipedia, Kevin has more obscure knowledge than he will ever need. Lucky for us, we have friends with similar mental prowesses, and most nights, we make a damn fine team (especially with entire categories devoted to knowledge of swords).
The pot for winning an evening of trivia can range from $60 to $120, depending on how many teams are playing that evening. If your team is lucky (and knowledgeable enough) to win, you walk away with a profit from partaking in this experience (or breaking even, at the very least). And even if you don't win, you have an enjoyable evening drinking and commiserating with like minded people. Always a positive in my book. Try brainstormer.com for a listing of pubs that hold trivia nights in your neck of the woods!