It really depends on where you live, and what you like to do... but for summer i would suggest somewhere with water (like a waterpark or ocean). If you are looking to not to travel to terribly far, then look up some fun waterparks for your state.....(:
Caribbean Cruise. vacationstogo.com has really good "last minute deals". I have used them before for a Princess Cruise for $370 for the whole week. That includes a beautiful room, transportation between the islands, all meals, shows, everything. It's the best deal.
Depends on where you live, your budget, and how far you're willing to go. For a tropical vacation with ocean you can visit Hawaii, Fiji, or one of those beachside cities like Miami. If you want to go on a cruise you can go on one of those Disney cruises( I hear they have a private island). One thing you should never do in the summer (and something I won't do either) is just stay at your house, eat, get a haircut, sleep, take a walk, walk your dog, over and over again. Hope this helps.
God's own country, Kerala is the best place for vacation in summer.. The beautiful hill stations, back waters, water falls.. etc makes this land wonderful. You can visit this link for more info about kerala tourist attractions - http://keralatouristdestination.wordpress.com/