Another thing that you can do is go to Amazon and type in the search box: toys for three year old girls, toys for five year old boys, toys for ten year olds, or any other combination you might need. This will give you a list of suggestions. I've found this to be quite useful.
You can type in the same kind of word combinations into Google and find websites like this: clicky-clicky
A time tested way of finding out possible gifts for kids is to ask their parents what they think their child might be interested in. We asked our son Ben and his wife Marie what kinds of things their kids might want and they gave us some direction--they said some kind of toys or activities that will help their kids to learn. This was very helpful.
All that being said, I've found that making sure you know the interests of the kids you are buying for goes a long way toward finding a gift those kids will love.
And now, here's a great song by the Oak Ridge Boys: Thank God for Kids