Looks like Mariah Carey's comeback is happening now.  She's just announced a free concert this Thursday, March 1 at New York City's Gotham Hall.  According to a note on her official website, you can score your tickets by going to the website PlotYourEscape.com now.  Tickets are limited, and it seems to be part of a big promotion featuring four concerts by four artists in four different cities.  Maroon 5 and Sara Bareilles are teaming up to perform in Chicago on the same day; there will also be shows in Los Angeles and New Orleans.  Footage of these shows will air on Jimmy Kimmel Live, according to PlotYourEscape.com.