Although Apple has not yet updated the iTunes Store front page to link directly to the desktop version of the iPhone AppStore, it can still be accessed with a little trickery. To access the desktop AppStore, follow these steps:
- Download and install iTunes 7.7, if you haven't already
- Click on the iTunes Store in the left-hand pane
- Search for current iPhone application, such as "Super Monkey Ball"
- Click small grey arrow next to Super Monkey Ball in the search results to go to the app's download page
- In the top navigation bar in iTunes, click "AppStore"
The main AppStore page will appear, and you can buy and download applications then sync them to your iPhone/iPod touch.
As noted by a commenter below, there's another method:
"go up to Preferences, under the General tab click to show the 'Applications' item in your menu, and then hit 'OK.' From 'Applications' in the left hand side is a link to ?Get More Applications? which will take you right to the store front."