I myself use Android (tablet and phone) and my favourite app is currently the AWD launcher EX on tablet... it has a hide-able dock which helps keep the screen clear and also has a few transitions etc to choose from as well as themes but all the themes I've tried so far mess up the dock image so I still use the stock one.
There's loads of apps I feel I have to install when I get a new android phone...
Advanced Task Killer
Android System Info (shows battery, memory and disk space in widget)
Apps 2 SD (stores apps on the SD card)
Circle Launcher Light (tidies apps on home screen)
Unified Remote (controls PC remotely)
Volume Control+ (volume lock and scheduler)
Where's My Droid (helps you find your lost phone)