Here are the Android Apps that I currently love. It’s not a complete list, but it’s a pretty good start.

Music and sound apps

Apps for when you’re traveling

TripIt: keep track of trips and plane flights for upcoming travel

Google Translate: translate tons of languages into tons of other languages. You can also do voice-recognition-to-text for English, then translate. This app will even do text-to-speech (voice synthesis) in many languages such as French, Spanish, Italian, and German.

Yelp: Find great restaurants nearby. Pro tip: scan the reviews to discover good dishes to order.

Compass: also handy when you’re traveling

Social apps

Twitter: official Twitter app for Android. This app can take empty/missing pictures in your contacts and populate your contacts’ pictures with their Twitter profile pictures, which is nice.

Seesmic: another fantastic Twitter app for Android

Google Buzz widget: an easy way to post to Buzz from your phone. By the way, I’ve noticed myself using Buzz more and more recently. When I started on Twitter, it took me several months to warm to the service. I think the same principle applies to Buzz. Buzz fills a nice niche between Twitter (microblogging) and regular blogging. It’s great when you want to throw out one quick idea, but you need more than 140 characters. You can read my Buzzes (or follow me on Buzz) if you want.

Cool demos / showing off

Google Skymap: move your phone to see where stars are. Like augmented reality for the sky.

Tricorder: shows all the different sensor readings of your phone. Includes accelerometer and tilt sensors, GPS and lat/lon, wifi, cell phone strength, compass, acoustic data–even solar activity.

Metal Detector: an app that detects metal. I still don’t know how it works (maybe it uses the magnetometer sensor that allows the compass), but it actually does work on many types of metal

Google Earth: most of the eye candy of Google Earth, but on your phone

LED Scroller: enter a message and your phone turns into a faux LED scrolling sign. Kinda low-tech, but impresses people more than I expected.

Hypnotic Spiral: makes a swirling spiral that you can control

The Schwartz Unsheathed: a light sword that makes cool sounds as you move your phone.

Signal strength apps

Wifi Analyzer: walk around and see a dynamic graph of wifi signal strength. Great for picking the right place to sit in an airport or cafe to get the best wifi signal

Antennas: shows a Google map with nearby antennas on it. Good for monitoring your phone’s signal strength

RF Signal Tracker (two versions, Donut and Eclair): another app to measure cell phone tower signal strength

QR Code and Barcode apps

Key Ring: scan your loyalty and other membership cards (e.g. Safeway, or your gym). Then use this app instead of carrying a bunch of membership cards around. I wish my phone could replace everything in my wallet.

App Referrer: shows all your installed apps. Click on an application and it will generate a large QR barcode on your screen that your friend can scan to install the same app.

Barcode Scanner: scan barcodes and QR codes. Very handy to install applications and visit urls. Note that the “Barcode Scanner” app (like App Referrer) can also show QR codes for applications — just press the options button. Can also show QR codes for contacts, bookmarks, and the clipboard.

Core apps / misc

My Tracks: records where you go using GPS and lets you upload a “track” to Google Maps

Navigation: get turn-by-turn directions as you drive

Movies: check movie times and see ratings from critics vs. audiences

Wheres My Droid: If you lose your phone and it’s in silent mode, this app will help you find your phone. I’ve tried Mobile Defense and that’s also very nice.

WordPress: Upload images and blog from your phone

Amazon.com: mobile shopping, plus add things to your Amazon wishlist

Shopper: Google app to scan barcodes and show product search results

BBC News: see the latest in world news. This is an unofficial widget.

News and Weather: customizable news, plus this app shows weather in your current location. Wish I could enter 3-4 cities and flick between weather reports though.

Weather: see the weather in multiple cities

Google Finance: check stock prices and news

Google Maps: see where you are

Google also offers a lot of mobile apps, but I just wanted to highlight my favorite applications.

Okay, those are my favorite Android apps, but what did I miss? Which Android Apps do you love?