Now you can browse or search for apps in the Android Market right from your web browser rather than only from your mobile device. You can still do that as well but now, you have two great choices.
According to Google, you can send apps directly to your Android device from the web, and you can share them with your friends via Twitter. And you can read and post app reviews directly to Android Market from the web or from your device.
One feature I especially like is ‘My Market Account':
[...] what about all those apps you’ve already purchased and downloaded? Sign in to the website with your Google account and click “My Market Account” to see all the apps you’ve purchased or downloaded. It makes managing all your apps quite easy.
If you have an Android device, you’ll want to check it out.