Basically, I'm not very good at singing, and the musical auditions are coming up in my school. I'm joining, that's for sure, but I want to improve quickly…and I don't have time for a vocal coach right now.
go talk to the choir teacher at your school, he or she will help for free.
and as for online. i'm pretty sure no because, it would be too hard to help people online, plus its alot of work for people to upload thier voice and all of the exersizes.