A perfect web-site to find a hotel, hostel or apartment in Kiev. Unfortunately, it's only in Russian.
This is a reliable choice to garantee the availability and price of the apartment on coming to Kiev. All apartments are in a perfect condition, and are located at the very center of the city (Hreschatyk, Palats Sportu etc), just 10 minutes away from the fest venue. Please mention "Kiev Spring Fest" while making a reservation.
http://central-kiev-apartments.com/
Another rental agency, with a large list of apartments at the center of Kiev.