We've been following the Bloomberg Philanthropies' Mayors Challenge since the city innovation contest (and the $9 million in total prize money that comes with it) was announced last summer. With an aim of encouraging "breakthrough solutions" in city governance, New York City Mayor Michael Bloomberg invited any U.S. city with a population of 30,000 or more to submit entries that would be judged based on their "boldness, strength of planning, potential for impact, and replicability" in other cities. Twenty finalists (out of 305 entries) were announced in November, and now the Huffington Post has collected testimonials and videos from the mayors of each city still in the running. Five winners will be announced this spring, but in the meantime the public is being invited to vote for their favorites. Of the 20 finalists, the eight ideas below struck us as particularly compelling. Which city do you think should win the $5 million first place prize?