Jose Luis Orozco has good CD's, as stated above.. he just came out with a DVD also. (matter of fact, if you decide on that, I can sell you ours cheap, as my kids could care less -there past that stage-)
The absolute best way for them to learn is to immerse them in it... watching the spanish channel is good, as they will learn the dialect early.
If you have migrant camps locally, you might consider a few things....
* Volunteer at the camp daycare/headstart
* Contact the church for the hispanics, and ask them if they know anyone interested in language trade (you keep 1 child XX hours XX days per week, and your child has a playmate, and learns spanish, while the hispanic child learns english)
There is always taking in a foreign exchange student.
and there are instant immersion programs available for the pc.