Here are a few websites that I hope are helpful.
Good luck. I'm sorry for the loss of your husband.
I'm a single mom with a 8 year old. My husband died 4 years ago, I'm employed, but my job ends 2 hours after my kids school lets out. I used to be able to get a babysitter, but money is tight and I can't pay her. I can't take off work forever. Help?
Try talking to your boss, maybe he/she will help by adjusting your work schedule so you can be home when your children come home from school. Or, like Tiger said, check into an after school program at the school, or maybe even your local community center.
Neighbors
Family members
Friends
After-school activities ... Or church groups ... Or clubs (YMCA, Scouts, etc)