Good thing you're coming now and not 5 years ago:
Chicago's Bean sculpture is free to photograph, at last - Boing Boing
I have no suggestions for gear, but there are so many things to photograph I wouldn't know where to start! That is, if you're interested in architecture.
A quick Google search yielded these results...
Flickr: Discussing Best Places To Visit/Photograph in Chicago...
Chicago Photo Ops - Chicago Photography - Popular Chicago Photo Spots
You could pay to go up the
Sears - er, Willis - Tower and get a
shot from above, but you can also go to the
Signature Lounge on the 96th floor of the John Hancock building. The view is
just as good (though no
glass balconies!) and there's no entry fee. You might want to get a drink or two out of respect though.
I know Star is interested in the museums too, so you should probably consider a
CityPass, in which case you wouldn't have to worry about the entrance fee for the Willis Tower SkyDeck. If you do this, I'd choose the SkyDeck over the Hancock observatory, because as mentioned above you can go to the Signature Lounge or Signature Room instead. In fact, the very first time I ever met a TFPer in real life it was for drinks at the Signature Lounge. If you do this, I'd do the SkyDeck for shots during the day time, and then get drinks at the Signature Lounge and take shots
there during the
night time.
Obviously there are a bunch of photo opportunities in the museums,
Sue at the
Field Museum being the most well-known. You can get
pretty good shots of the
skyline from there too. And, of course, there's the
Art Institute.
Marina City is another fairly iconic image of Chicago, and the Chicago Riverwalk is nearby too.
Lincoln Park Zoo and
Conservatory is
free to enter, and while it's not the best zoo ever it's pretty decent and it's kind of cool to see the
animals with the urban backdrop.
Navy Pier is a
tourist trap, but people seem to really like the
ferris wheel. I imagine there are probably
some good shots from
there, though it obviously costs money to ride. I think Navy Pier itself is free to enter, so at the very least you could try for some
skyline shots from there if you want.
One of the better spots to get a shot of
the skyline - unless you're on a
Lake Michigan boat ride - is from
right around the
Shedd Aquarium and/or
Adler Planetarium. Again, there are good shots here during both daytime and nighttime. Belmont and Diversey Harbors or North Avenue Beach are also decent spots for
skyline shots from a different angle.
Buckingham Fountain and
Grant Park are good places to go, and the Hyde Park neighborhood has some great
older architecture (including the
University of Chicago and
President Barack Obama's house) and I think it's totally worth a visit if you like that sort of thing. It's right near the
Museum of Science and Industry if you're interested in that. Also nearby is
Promontory Point, which is a
popular spot for photographs. Since you know about "
The Bean," you've got
Millennium Park covered.
There is, of course, a trail to walk down pretty much anywhere you go along the lake, so there are
plenty of
opportunities there.
Not too far from Amy's neighborhood - but a bit of a trek from where you two will be staying - is
Baha'i Temple, which is another landmark of the area.
By now you're probably getting the idea... there are just too many good spots to list! And I've pretty much only named the more popular places. Best thing to do is just grab your camera and explore!