Campanello's is a good italian restaurant about a block from the convention center. It's an old mom/pap restaurant that feeds you a lot of food for the money.
Penn Station is my favorite lunch. There is one downtown somewhere. Awesome subs and the best philly cheese steak I've ever had
Skyline or Camp Washington Chili like Lonnie said for some Cincy chili....Camp Washington is not too far from downtown. Only one of those, and it was on man vs food last year. Skyline chili's are everywhere and probably 2 of them downtown. Gold Star chili isn't bad either. Get a 4 or 5-way (chili, cheese, spaghetti, beans, onions) or a cheese coney (hotdog, chili, mustard, cheese.)
Montgomery Inn "The Boathouse" is an upper scale bbq place. Good ribs...probably not the best ever but the atmosphere there is pretty cool.
Hofbräuhaus Newport is right across the river. Some good german food, fun and beer. Everyone dances on the tables later in the night....always makes for a fun night.
Stay away from the hooters in newport...it's nasty!
There are a ton of little mom and pa restaurants in Newport, Kentucky on Monmoth St, right across the restaraunt. Newport used to be a big mob town too. Pretty cool history there.
Union Terminal is an old train station turned into a museum right outside of downtown. If you like old buildings, check it out, especially if you like art deco. They have an imax theater there with a pretty good movie right now about the canadian pacific railroad.
Newport on the Levy, right across the river, has a real nice aquarium and some restaurants including duey's pizza and an irish pub/restaurant ...good stuff.
If you like ice hockey, check out the cincinnati cyclones schedule. they play at the coliseum in downtown. It's a minor league team but makes for a nice cheap night...often have $1 hot dog and beer nights.