There are endless possibilities!
I am an "afterschooler" with an accelerated child (DS 6 years). I do not follow a complete curriculm, but use the concepts from them to teach my child. Needless to say, I used my free time to "challenge" my child rather than depend on his PS for doing a good job of it. Though my child has moved on to a better school now, I continue to do the afterschool acceleration, but at a slower pace.
Here is the list of choices that might help you:
Math - Singapore Math with it's whole suite of books, Miquon math with Cuisenaire rods
Math online - EPGY math, DreamBox math, DragonBox math, Khan Academy
LA - Start with First Language Lessons and move on to MCT's Grammar Island. Spelling - Spelling workout, Literature - real literature read alouds, Poetry memorization of funny poems because DS loves that kind of stuff.
LA online - EPGY LA
Handwriting - our weakest area - we used Kumon books that were great but proved ineffective in the long run. So, you might check Handwriting Without Tears that others have recommended.
History - we have done small units on American history based on interest. Will be starting Story of the World or A Child's History of the World in 2nd grade.
Science - Building Fundamentals of Scientific Understanding and various interest led topics like electricity, volcanoes, tubers and rhizomes, robots etc with books from the library.
Music - Faber Piano Adventures (outsourced to a music school)
Art and Craft - no skills here ... so can't suggest anything.
Extras - Chess - outsourced to chess school, but I will help with chess homework. Susan Polgar's book is pretty good.
Have fun chosing!