We were going to rent a house at a local beach for the week. Bring your own food and drinks and just hang at the beach. Around here that is about $1,000 but thats is for a 4 bdrm house and we were going to split the cost with family friends so we'd each pay about $500 for the week for the 4 of us, plus food, no travel costs and not much in entertainment costs. There are shows on the beach that are free, free fireworks one night a week.
Also if you can find a cruise line that leaves from where you live, like Norweigen cruise line cruises out of Boston from early May to late september - ish... its like $500 for a 7 day cruise to Bermuda with no air fare! A cruise includes all your food, so if you can watch your discretionary spending you can do a cruise for pretty cheap if you don't need to fly!
Also camping for a long weekend... its about $20 a night for a campground. If you have all the equipment already that is a cheap and fun get-away if you like the great outdoors!
