It was called the Cubby Den, I believe.
Cubby Bear.
1. Take in a Cubs game or go to Wrigleyville if a Cubs game is on - Cubby Bear is across the street from the front entrance (homeplate) to Wrigley. That street has good bars up and down it (I believe it's Clark St. - runs down 3rd base line). Murphy's is directly opposite of the Cubby Bear (behind Center field) (I believe it's on Sheffield).
2. Go to the Cubs game via the "L". The L is the elevated train/subway. Take the Red Line and get off at the Addison stop - within a block of the field.
3. Hit a great Chicago steakhouse. Hat named some. There are several good ones.
4. Hit a great Chicago pizza place. Geno's and Giradano's are landmarks. The deep dish takes about 45 minutes to cook so be prepared. Lou Malnati's is one of my favorites.
5. Shopping? The Magnificent Mile is the place. Just north of the Chicago river and the Loop. I believe it's Michigan Ave.
6. Sightseeing? The lakefront is very nice. You can start at the Art Institute. Directly behind that is Grant Park (the fountain from Married with Children). Soldier Field, the Field Museum (Natural History) and Shedd Aquarium are all slightly to the south but walkable from Grant Park.
Make sure you see where the Chicago river empties out into Lake Michigan. It's right downtown (the Loop is to the south and Magnificent Mile is to the north). Lot's of great architecture (Wrigley bldg., the twin spirals condos, and the bridges are cool).
You'll recognize a lot of what you see from movies etc.
It's worth a trip up to the observation room in the Hancock bldg (on the Magnificent Mile). Pretty cool and amazing view. I haven't done the Sears Tower (in the Loop).
7. More sightseeing? The Lincoln Park Zoo is nice. It's further north in the Lincoln Park area (very nice). Cool little zoo on the lakefront and close to several parks, beaches and marinas.
8. Nightlife? Everywhere. Hat mentioned Rush St. Definitely a lot of action there. Rush and St. come together. Division is a cross street. Can be a little touristy but definitely worth a night. Otherwise, there are lots of little pockets of neighborhood bars and restaurants. Generally, these are all north of the Magnificent Mile. There is an area right around Ontario and Ohio that has a Hard Rock, a Rock Bottom Brewery, etc.
Navy pier is another area (just north of the river and on the lakefront) that has a lot of restaurants, bars, shopping and amusement rides in one place.
9. Eats? In addition to the steak and pizza have a:
Brat, chicago-style dog or Maxwell St. Polish sausage.
Italian beef sandwich (w/ giardiniera a pepper relish).
Old Style (beer)
Leinenkugel (Red or Original beer)
10. Music? Lots of great venues. Many blues clubs (Buddy Guy's, Kingston Mines, etc.) and many good venues (Riviera, Metro, Aragon Ballroom, etc.)
Overall, Chicago is safe, clean, entertaining and an all around good time.
Enjoy.