If you went last year then you probably already saw the "must-see" stuff. If not, here is some things to see in Kiev:

• The Kiev Pechersk Lavra (tip: there are unofficial "guides" wandering around and if you find one that speaks English, or whatever you native tongue is, get him to show you around)
• St. Michael’s Golden-Domed Monastery
• Saint Sophia Cathedral
• Chernobyl Museum
• The WWII Museum and Park and Defense of the Motherland Monument
• Go shopping along the Andriyivsky uzviz (protip: practically every WII German item you see will be fake)
• Take the metro and marvel at how far underground it is then realize you're also in a nuclear bomb shelter
• See what 70-odd years of Soviet rule does to a what used to be beautiful city.

If you can afford it, take the Chernobyl/Pripyat tour.

The last time I was there, there were several packs of feral dogs running around. they pretty much leave you alone but I suppose getting a rabies vaccination beforehand would not be a bad idea.