I have not checked out any online photo classes, so this is just my thinking. I would think anything you could learn in an online class, you could also learn from buying a book. I would also find a local camera shop or somthing, and try and get to know them. when you are in buying film or what ever you can get there input on things or tips and such. Now on online class could have its benefits as well. A larger commuity to talk to about your pictures and a teacher.
Again I dont how online classes work, but any "in class" classes i have taken we develope and print our own photos. I think this is a HUGE part of photograph other than just shooting the pictures.
Now if it is digital you want, then I think an online class woould be fine, still more $ than a book.
Like I said I have not looked at any online classes, so if I am wrong about anything or other people have different thoughts....