Getdeb and Playdeb are both discontinued. The mirrorsite you can still use. However, even the mirrorsite will be outdated after a while. On the other hand, all the packages which were available on Getdeb are freely available. If you want e specific application, first to look is Software Manager to check if it is available already in the Mint repository. Secondly, you could ask here if anyone has a link to the website of that application you wnat. Third, you could look for it yourself on the internet if you know the name of the package.
A good place to start is here: http://www.linuxappfinder.com/
and even this site has some applications: http://ubuntu-tweak.com/
. In my opinion there's not much of a reason to have a site like Getdeb since all applications are provided to users one way or another. The problem for site owner is keeping everything up-to-date. With each new version, the site owner/maintainer must update the site as well. This was basically the reason for the Getdeb owner to quit the job, lack of time to keep the site up-to-date.