As of yesterday, Google's Android Market is accessible via a website that allows you to browse, download and even buy Android applications that are then forwarded to your mobile device. Google has also announced that it is working on in-app purchases as well.
If you own an Android-based device you already know that apps were previously available only via the the device itself, but now all that is changed as you can now browse all those apps quite easily in front of the computer screen. Of course, you still have to log in with your Goggle Account and those chosen apps will be OTA (over the air) uploaded to your device.
On a similar note, Google has announced that it will implement a in-app purchase pretty soon, and by the looks of it, the UI of it looks a lot like the new Android Market and should be pretty easy for developers to implement it in their own apps.
You can check out the Android Market site here.