Pretty much anything on 4th or University is good for food, bars, shopping, etc. That's sort of the "it" place in the city.
If you want a lighter meal, a good non-alcoholic drink, baked goods, or some nifty candy, I highly recommend the Chocolate Iguana on 4th. That's my favorite place.
If you want a huge greasy (but very good) burger from a place that's been on tv (man vs. food), DH recommends Lindy's on 4th.
The Auld Dubliner on University is also a cool, underrated place for food and drinks.
Which Wich on University is also pretty neat, especially if you've never been to one before. It's sort of like Subway, but seems to be of a higher quality.
For a really nice Sunday breakfast buffet, Sweet Tomatoes on Broadway is my pick.
If you're in the bar fly mood, The Hut and Sky Bar, both on 4th, are pretty cool with a laid back atmosphere and not too much crazy party stuff. If you want crazy party stuff, Maloney's on 4th. Risky Business on Craycroft is good for light appetizer type food, and they also some very good unique drinks.
As far as things to do...let's see...
If you want to be outside:
Reid Park/Reid Park Zoo on 22nd are nice. The zoo is small but a nice day trip.
A day trip up to Summerhaven on Mt. Lemmon is worth the longish drive. It's a cute little town at the top of the mountain with a few little shops. I highly suggest stopping into the Cookie Cabin up there. There are also some amazing views along the drive.
Tucson Botanical Gardens...I believe their Butterfly Magic exhibit should be open now too.
Old Tucson Studios. It's a wild west themed "park" that they shoot a lot of movies at. Pretty cool.
Traildust Town on Tanque Verde. A bit lame, and only worth about an hour. But there's a nice candy store with old fashioned candy and a very nice steakhouse.
Inside stuff:
Pima Air and Space Museum. I've never been but i've heard good things.
The problem we've run into with Tucson is that there isn't a lot of "indoors" things to do here. It's a very young, active, pedestrian city so it tends to be more outdoors oriented. Which is fine, this time of year lol. If I think of anything else I wil add it in.