Our schools have no G&T until 3rd grade, so DD just started the program. We are still trying to get a sense of what DD will learn from the program, but so far we've heard great things from the parents of the older students in the program. DD seems to be learning much more than she was before the program started, so we are feeling hopeful that this will help meet her educational needs. Up until now, we've been trying to keep her supplied with LOTS of books (she is a voracious reader - fiction and non). We've also signed her up for many extra-curricular science and enrichment courses. IXL, mentioned by blackcat, is actually used by DD's school, too, and she has permission from her teacher to work ahead of 3rd grade. DD also plays chess and an instrument.
I draw, too, so art lessons up until now have been at home.