I use Multimedia Fusion Express! It is good if you're not into programming. You simply lay down the title screen, levels, ending, then you plop on the backgrounds and platforms, add the characters, and you're done!
An extremly rare and valuable Yoshi!
"Who want''''s to buy a gold Yoshi? Selling Price, $99,999,999,999,999,999,999,999,999,999,999,999,999,999,999,999,999,999,999!" (almost 10 Googols!)