I lived in Charlotte for a few years. My favorite karaoke in town was at Steamer's on the northside. Very blue collar bar with lots to do (fooseball, pool tables, trivia, arcade), including karaoke on Friday and Saturday nights:
http://charlotte.citysearch.com/profile ... t_pub.html
Also try Midtown Sundries on the South Side in Rock Hill. More of a college bar. I think they have karaoke once in the middle of the week and one day on the weekends. There are like 7-8 more Midtown Sundries in town, but this one has the best karaoke.
http://maps.google.com/maps/place?hl=en ... 0038278721
Charlotte as a whole is a pretty yuppie town with lots of young professionals, and it is actually pretty hard to find a good blue collar bar with unpretentious karaoke. Both of these are about as good as it gets unless you like hanging out with rich kids in their late 20s/early 30s.