If you want some real nice ambient sounds, go check HGFortune VST. Most of them are free and play flawlessly in Mixcraft. Thousands of presets and the possibility to create and save completely new ones. Not complicated, tweakable at will, and you can add Soundfont banks to most of them. Lazy? Use the buttons! Some even come with new patches with more new sounds!
Nice quality synths for nothin'!
That guy is simply a genius.http://www.hgf-synthesizer.com/
...And the others are very affordable.
I don't know if this was already mentioned but here it is (again?).