There have been plenty of articles written around the web about the top or best Android apps. I always find these lists very subjective but they are at least a good way to share what you've found and a great way for other users to discover new apps they've not tried yet. I've been using an HTC Desire for over six months so I'd consider myself a reasonably experienced user now. It's a world away from the Nokia N73 I was using previously and my first foray into wifi-enabled portable touch screen devices (for personal use anyway).
Rather than bother myself considering which is the most useful, here's an alphabetical list of the apps I'm using right now. I'd love to hear what other people are using for similar things, there's so many good apps out there I'm sure to have not checked them all out.
Angry Birds (Game)
There's loads of games on the Android platform but this is the one I've spent most time playing. I'd be very surprised if you haven't come across it by now but if not then give it a go.
Barcode Scanner (Bar Code Scanner)
When I first got the phone I really didn't see the point of having a barcode scanner. It has, however, proven quite useful on occasion. I've yet to use it to scan any tangible product in a shop for example. Where it does come into its own is opening links from the web on your desktop in your mobile browser. I have, on more than one occasion, now come across sites that provide a QR code (2d bar code) that gives you a link to a web page or even better gives you a link directly to the right app in the marketplace.
eBuddy (Instant Messenger)
A multi-protocol instant messenger for Android. It connects to all the instant message services I use and gives me a nice way to increase the amount of time I spend logged into them so I can still be contacted even when not directly using a computer. I use a multi-protocol client on my desktop so it's great to find a decent one on the mobile platform which means you don't have to run individual apps for each of the services you want to log into.
ES File Explorer (File Manager)
The version of Android I have (2.2 from HTC) doesn't come with any sort of file manager or mechanism for installing APK files. ES File Explorer is excellent for both of these tasks. It's the best and most flexible file explorer I've come across but for some reason isn't the most popular or widely known/used. It has some neat advanced features such as the capability to connect to files over FTP/Samba and integrated bluetooth, etc. A real step up from any of the other file managers I've seen on Android.
Google Reader (Feed Reader)
As I write Google have just released the official app for their Reader service. It's definitely an improvement over the mobile version of Reader in the web browser so I'd recommend it just for that. However, it also seems to be (IMHO) better than other popular reader apps such as Feedsquares. Personally, Reader is the only internet based feed reader I use so having something integrated to it on my phone is fab.
Google maps in an app. You've almost certainly already seen it, but I still use it a lot and like it so it makes my list of useful apps.
RAC Traffic (Traffic/Navigation)
This is one area where I've not searched around much for other apps in the field. The RAC traffic app shows you where the traffic hot spots and problems are on roads in the UK. It's really useful to check this (when I remember to do so) before going off on a longer journey in order to help pick the best route that day. I'm sure it can't be the best app out there for this sort of thing so would be interested in hearing about others too.
Scrobble Droid (Social Music)
I find the last.fm service on the Internet a really useful way to discover music and share music with friends. I don't tend to use the last.fm clients to listen to music very much so that app doesn't feature on my list. However, this is a really tiny but useful app (more of a utility really) that will send the tracks you play in the Android music player to last.fm. This means anything I listen to on my phone gets added to my last.fm account and helps build my profile on the site.
Skype (Instant Messenger and VOIP)
Either you use Skype or you don't and you know what it is or you don't. The official client for Skype on Android seems to be pretty good to me and a neat way to make free calls to friends over your wireless network.
Todo List Widget (Productivity)
I've tried several todo list apps and widgets on Android but essentially wanted something stupidly simple that would literally just shove a list of stuff on the desktop and allow me to add/remove/tick off items as I deem necessary. Through a recommendation from a friend I found a widget called "Todo List Widget" which does just that, it's everything I wanted, very very simple and easy to use. If you want something advanced or more pervasive across devices this isn't the one for you, check out something like Remember The Milk instead.
TweetDeck (Social Client)
I've ditched the Facebook and Twitter apps in favour of using the same app on the phone as I do on the desktop. I've never experimented with Adobe Air but TweetDeck seems to be a great example built on that platform. I find TweetDeck much more usable than the other apps and it does seem to just work, is intuitive and nice to use. Once again a great user experience wins the day on the mobile platform.
Ever tried watching videos in the web browser, they're rubbish right? The bulk standard youtube app sorts this out nicely, giving a much better view and size of the video and easy to use controls.
I found some other useful apps on my phone too that I have used briefly but can't necessarily recommend with the apps above because I've not used them extensively enough. These are "AndChat" for IRC related chats, it seems to be very similar to xchat but for Android; "c:geo" for Geocaching as it appears to be a fully functional geocaching app you can use out in the field while caching; and "Gesture Search" which is a Google app which allows you to very neatly search for things (apps, contacts, etc) on your phone via gestures.
In full Trevor McDonald style I'll sign off this post with an "And finally" thought... wouldn't it be really useful to have a social market place where you can suggest and rate apps to friends? The ratings system in the market place is all very well but isn't particularly relevant to me. My friends and contacts know me best and I respect their recommendations much more than a generic ratings system. This sort of functionality would certainly remove the need for this type of blog post entirely.