Great shots...My kinda shots...I'm guessing they're still untouched...There's a great photoshp tutorial somewhere online entitled "Jazzing Up Your skies". Your skies are already great but u can still toy with them a bit...
I really love the compositions of Photos 1 and 3! They make me say "Awww" and "Wow" all over.
Of course, the colour of the sky and the palm tree silhouettes are very impressive in all of them, but those two do stand out for me.