This is one of the best spelling sites that I have come across, and it's FREE!!
SPELLING CITY offers you the capability of typing in all of your spelling lists.
It teaches, tests, and has games galore to trick your kids into thinking they are having fun. :)
I use it for my 5 year old with her sight words, and have even insisted that my teen refreshes his spelling with some advanced vocabulary words.
Enjoy - I have made it a regular part of our school day for those times when I just need a little distraction.
*make sure you set up a user account so that you can save all of our spelling lists. Great for weekly review.