I have recently used Ice Cream Sandwich and I really like the Holo theme. I would like to be able to use this theme for lower Android API versions (Gingerbread, Froyo, Eclair, etc). Is there a way to port this theme to older versions of Android, or any other way that I could use it?
There are Holo themes available for the T-Mobile/CyanogenMod Theme Chooser. If you have the theme chooser you just download a Holo theme from the market select it.
You can find out more about CyanogenMod (has the theme chooser built in) here.