The Ice Cream Sandwich firmware [Android 4.0] comes with a lot of goodies, one of them is the clock widget if you like it then you can have the same clock widget for your current Android firmware too, Zer0_Cool from XDA forums has released an modified clock apk that looks just like that. Download from below.
Android 4.0 clock apk download for older Android firmwares
Download link. Thread link.
The original transparent clock widget on which this apk is based can be download from this Market link.