Google Voice – For me the “Must Have” application. It allows me to send and receive free SMS from my phone and do Voice Mail to text conversion, totally integrated with the phone.
Listen – A wonderful Pdcasting application, I use it every day.
Tricorder – It actually works and looks like the display on Star Trek Tricorders.
Bubble – Make your phone into a bubble level, handy if you need it.
Fandango Movies – A great way to see what movies show where in your city. I don’t actually use it to buy tickets.
TaskPanel – A great tool for monitoring and kill tasks on Android.
Aurora Universal Search – lets you search the whole phone for Contacts, Calendar, Applications, Meda, SMS/MMS messages and files on the SD card.
Compass – A really nice Compass program.
WiFI Analyzer – A nice tool to see what WiFI networks are near you and how strong the signal is.
Issuu Mobile – a fun tool to read over a million different magazines for free.
Battery Widget – A nice widget right on the screen to show the real state of your battery.
Tip Calculator Widget – A stupidly simple and easy to use tip calculator that even includes the ability to split the bill after adding the tip.
RealCalc Scientific Calculator – A great RPN or infix calculator.
Facebook for Android – A handy way to update your Facebook status.