If you're using Centrafuse 3.x and you are having trouble finding your favorite apps through the Market app within Centrafuse, this is because only the latest version of compatible apps will appear for download, depending on your Centrafuse version. This means that if, for example, you want to download the Email app and you are running Centrafuse 3.6, it will not appear because Email was updated to require 4.x.
To access these older app versions all you need to is visit the Online Market and drill down until you see the "Click here to download previous versions" link. This will show you a list of previous version of any app. This is also very useful if you want to "rollback" to a previous version after updating an app that's not working well any more. To do this, just remove the new app from your Market app browser and then install the previous app package downloaded from the Online Market