Justin Angel put together a blog post on reverse engineering Windows 8 applications and he described the locations of the APPX packages on the local machine. Although working well for the Developer Preview, the application locations are no longer the same in the Consumer Preview. Compare those for yourself:
By the way, if someone attempts to open the WindowsApps folder with the default user, an error message will be shown with an Access Denied problem. To mitigate this issue, you have to change the owner from TrustedInstaller to the current user (the method described by Justin Angel above works).
Does changing the owner mean that I won’t be able to install apps from the Marketplace?
I am deploying my application from Visual Studio 11 Beta. Is it also installed in WindowsApps?
No. It is located in your project folder: C:\Users\<USERNAME>\Documents\Visual Studio 11\Projects\<SOLUTIONNAME>\<PROJECTNAME>\bin\Debug\AppX
It is worth mentioning that the package deployed from Visual Studio 11 Beta, although located in a different area of the user disk space, will still be registered in line with all other Metro applications in the Windows Registry: