Action bar support is present in api 11 of android. We can support it for early versions of android with different libarires.
GreenDroid : https://github.com/cyrilmottier/GreenDroid
Use ActionBarSherlock. It is based on ICS code, is actively developed, and will use the native actionbar when run on ICS. It also plays nicely with the compatibility library and will let your use ICS features such as the split action bar and share providers. Probably the biggest plus is that it uses exactly the same API as ICS. If you don’t need fragmetns, you certainly don’t have to use them.
Green Droid offers a custom look and feel, not exactly consistent with Android UI design guide lines. Android-Actiobnar is based on custom layouts and only offers basic features.
Here’s a discussion (might be biased, since it’s by the ABS author):http://corner.squareup.com/2012/05/actionbarsherlock-as-a-base.html
A good link in support of ActionBarSherlock : Action bar support for early version of android