One of the most important pieces in the Android ecosystem is Android Market — Google’s application storefront that comes pre-installed on the vast majority of Android devices. Yes, there are third-party markets (Amazon launched a rival in March), but with 4.5 billion app installs so far, the official Market is where most of the action is. Today at a breakaway session at Google I/O, Eric Chu took the stage to walk developers through some of the key trends on Android Market, and to announce some new features that will be coming soon.

The biggest user-facing changes involve both the web and client versions of Android Market. The web version now features a dozen new lists that showcase various applications, including, ‘Trending’ and ‘Top Grossing’ lists. Market will start suggesting apps based on your previous downloads. And the Android team is taking a more active role in flagging the best apps — there are new badges that top developers can earn for producing consistently good applications, and an ‘editor’s choice’ badge that can be placed on individual great apps. All of this is designed to help both users and developers weed through the noise.

The client version of Market on Android devices is also getting an update that will include many of these new discovery features. The visual design looks significantly better than the current app, though I haven’t gotten to try it out yet. You can see a screenshot above. It wasn’t clear when this new client will roll out — I’ll try to get more details.

Unfortunately it doesn’t look like the web version of Market is getting a redesign (which I think it badly needs), and there wasn’t a discussion about the Tablet version of the Market client (which I think is plain ugly).

For more, see my notes from the presentation below:

International market is really picking up. Last year this time 70% of device activations were US, but now over half are abroad. US is around 40% of app consumption of Android Market. The take-away: the US is very important, but so is international.

“Android users love games.” “Android users are more technically savvy — they’re interested in tools that add more utility.” Productivity has remained a top category since the beginning, but a few apps represent bulk of revenue. These are relatively expensive apps that do well.

Starting today, based on the manifest of your application, you can upload published or draft app and see which devices it will be visible to. You can also opt out specific devices.

Another feature: in some cases devs have multiple versions of the same app for different products. Starting in June will launch multi-APK. Devs can have different versions of the app for different platform versions, screen sizes, texture compression formats — avialbale as one product listing. All the user ratings, comments, billing are aggregated.

Launching support for large apps in June. Support up to 4GB — Publish 50MB app package and up to two 2GB archives. Android Market will host these files. Market will manage the download and install of the archives.

Want to make it easy to launch marketing in products. One-click entry to AdMob campaign setup from dev console. Doesn’t touch the APK, but helps set it up.

Now have sales reports back to Jan 2010.

Starting today, adding new page on Android Market webpage called ‘Trending’. Lots of downloads in a short period. Also launching two more lists: Top New Free and Top New Paid. Refactoring existing Top Free and Top Paid to focus on most popular apps. And, a big one: Launching Top Grossing list.

Starting today these lists will be regionalized for top countries around the world.

Adding ‘Users also viewed’ and ‘Users also installed’

Will feature personal recommendations based on your apps

Starting today, launching Editor’s Choice. This is aimed at providing consumers information making it easy to find the best apps. Also launching Top Developers — top devs who make great apps consistently will be highlighted. See screenshot below.