Read through resolved questions for many discussions of what to do in Cleveland, where to stay, etc..
Popular attractions include: the Cleveland Museum of Art, one of the nation's best and with still free admission to its permanent galleries; the West Side Market, one of the last great public street car markets; the Cleveland Orchestra and Severance Hall, both among the world's most acclaimed; Holden Arboretum, one of the nation's largest and best, just east of the city; the RainForest exhibit at the Cleveland Metroparks Zoo; Playhouse Square, the largest performing arts center in the U.S. after Lincoln Center in New York City; Indians baseball at Progressive Field and Cavs basketball at Qucken Loans Arena; the Cleveland Botanical Garden, again a superb facility; several outstanding concert venues, including the Blossom Music Center inside the Cuyahoga Valley National Park; and some architectural gems, such as The Arcade.
http://www.tripadvisor.com/ShowUserReviews-g50207-d272156-r50557056-West_Side_Market-Cleveland_Ohio.html#REVIEWS
All of the above are discussed in other resolved questions.
There are many fun or exquisite restaurants, most very reasonably priced given their quality. Among the best IMO include Lola's on East 4th St. (everything in that entertainment district is very good IMO), the flagship restaurant of Iron Chef Michael Symon, the 2009 Great Lakes region James Beard award winner; Blue Point Grill in the Warehouse District for fish; Great Lakes Brewery on W. 25th St. a short walk from the West Side Market for beer; Momocho, an acclaimed "modern Mexican" restaurant in Ohio City; and L'Albatros Brassiere + Bar in University Circle, named by Esquire as one of 10 best new restaurants in the U.S. in 2009 (the trout there is a favorite). There are many other enjoyable restaurants.
http://www.nytimes.com/2009/07/08/realestate/commercial/08fourth.html
http://www.east4thstreet.com/home.php
BOL for an enjoyable Cleveland visit!