No jailbreak required
The website is
This method works for most apps and is updated with new content regularly. Most of the apps downloaded will connect to the Game Centre automatically.
This works with Mac App Store AND iOS App store as well.
If there are apps that aren’t there go to these websites and check there;
If the app you want is still not there, you can try torrenting it
Use thepiratebay.se or katproxy.com
Of course, try to support the developers by buying their apps as much as you can, only use this if you cannot buy it for some reason.