My Mom and Dad divorced when I was little and she raised me alone. I'd like to have a 'Mother-of-the-Bride' dance instead of 'Father-of-the-Bride' dance at my wedding reception. Is this appropriate?
Yes, it is very appropriate to give an Honor Dance to your Mother. Traditionally, it's commonplace for two ladies to Waltz and Polka together, but these days, ballroom dancing has tried to keep up with the times, and two ladies may even compete together at some DanceSport events.
Choose a song that has meaning to both of you, bring it to your ballroom dance instructor, and learn a few simple-yet-elegant steps to help you show your appreciation to the most important person in your life (up until now :-). It will be a memory she'll cherish forever!