This is a a list of Android applications that I currently have on my phone. Some are more often used than others, but all are useful.
These apps are running on my Sony Ericsson Xperia Arc, which has Android 2.3.3 on it. Most of them ran on the Sony Ericcson Xperia X10 as well.
ADW Launcher is a fast and feature rich home application replacement. Use it instead of Sony Ericsson's TimeScape and your phone will feel faster.
TweetDeck is the application that I use for Facebook and Twitter.
Dolphin Browser HD is my browser of choice. It provides a nice customizable startup screen with oft visited websites. It also has lots of plugins available for it, and supports gestures.
My Tracks is a great app for recording GPS information, and then uploading them to Google Maps later, sharing them with others, or keeping them private.
Barcode Scanner is a useful UPC and QR barcode scanner that would provide you with more information on what the barcode is (a product, a URL, ...etc.)
WeatherEye is the app for The Weather Network, which provides the most accurate forecasts for Canadian cities. Make sure you enable the alert feature so you are notified of weather watches and warnings.
Light Flow is an indispensible utility that allows you to customize the LED, sound and vibrate notification for many events and apps (e.g. missed call, missed SMS, Calendar, Gmail, ...etc.) Note that this is a paid app, but there is a Lite version that is not paid but supports less applications (e.g. no TweetDeck).
Silence Scheduler is an indispensible tool that silences the phone when you sleep, and turn on the sound back at a set time.
Quick Settings is a great utility that provides easy access to many of the phone's functions without being lost in the Android settings menu.
Aldiko Book Reader is a good ebook reader, with access to some of the Gutenberg Project's free books, without the need to register, like other readers.
Astro File Manager is a file and process manager. Useful to browse your SD Card, backup your applications, and much more.
Bubble is a bubble scale.
Compass is a magnetic and GPS compass with many modes.
Swiss Army Knife contains a compass, bubble scale, ruler, stopwatch, timer, and a flashlight tool, all in one.
ConnectBot is an ssh client. What is annoying is that it assumes that you have a trackball, and very few Android phones nowadays have it. The trackball when pressed is the Ctrl key. You can work around it in a cumbersome way by tapping the screen and tapping the keyboard icon that will appear.
Google Docs provides access to your Google Documents on your phone.
Google Sky Map is a very informative astronomy aid.
GTasks provides integration with your Google Tasks.
Advanced Task Killer allows you to kill pesky programs that insist on running all the time.
LED Light allows you to use the phone's LED as a flashlight.
3G Watchdog will tell you how much data you are using, and when you will run out of your plan's allowance.
Meebo IM, a multi service client for Instant Messaging (Yahoo Messenger, MSN Messenger, Google Talk, ICQ, ...etc.)
Skype should be self explanatory. If only it is not such a resource hog ...
TuneIn Radio a nice application that allows you to listen to hundreds of radio stations from around the world, categorized by genre, language, current location, ...etc.
Wifi Analyzer is a nice tool to show you information on Wifi networks around you, the channel they are using, signal strength, ...etc.
Wifi Fixer is a nice tool to get around an annoying bug in Android 2.3 that exhibit itself with certain networks, where the phone would disconnect then try to re-associate with the access point and hang in that state. This tool will get over that hang automatically.
Xperia X10 Hidden Gallery is a utility to unhide the built in gallery in Sony Ericsson Xperia phones, so you can have an icon for it.
Tape-a-Talk is a handy voice recorder.