I found Frankfurt to be VERY VERY BORING!!! Really not much to see there. The only thing I can think of is this old church in the old city center (1 of the only building that wasn't bombed during the war). If you like modern architecture, there are lots of office towers and stuff, if that's your thing.
For Moscow, try to check out a Circus there, it was pretty cool/neat. Also, 1 of the coolest areas I went to was VDNkH (
http://en.wikipedia.org/wiki/VDNKh). It was like this showplace to the world of how awesome communism is and stuff, was pretty cool to walk around there. Also there are some fleamarkets that were cool to check out, got acouple of those Russia Wolf hats there (and a rabbit fur one).
The only other thing we did all the time was get a bunch of beers and vodka and drink in red square at night. Just don't get too hammered and wander around the alleys, some russians tried to mug us at gun point.