We know that Kobo Vox will launch with the GetJar app store App on the device, but it is absolutely not the only place to get Apps. Here are a few links to get us started.
You can install from the device itself if you use their App.
This site is a good point of reference because the apps listed are designed to work well with tablets. Android 2.3 started on phones and many of the available apps look pretty lousy on tablets. The links are to Android Market (which the Vox will not launch with) but they can be obtained elsewhere.