You might want to check out noteflight, and a software program called Sibelius. Noteflight has a free edition, and then a subscription charge for more advanced features. I'm not sure about Sibelius; our school subscribes to it, but there might be a "lite" version for free.
Both are helpful for composing, arranging and/or transcribing music, and you can save a limited number of compositions (more with the paid version of noteflight, but we haven't gone there).
I think there is an old thread about music composition around here, but I don't think it focused on resources, IIRC.
