Here is a link to an online calculator that can not only give you an answer, but also show you the steps to take to solve the problem.
Another website that we mentioned in class was the Khan Academy. They have lots of videos that cover all subject levels, and all grade levels.
This site has a lot of video lessons on most of the topics we will cover in class this year.
Here is an online lattice calculator that will allow you to check your lattice multiplication.