It would be handy if users could have the flexibility of browsing the portableapps.com website with the convenience and ease of use of having the portable apps platform perform the downloading/installing.
A possible way to achieve this could be the use of Magnet URI links on the download page of applications on the website specifically for users wishing to download and install an application with the platform.
Clicking the magnet link would instruct the web browser to open the requested link with the portable apps platform which would perform the downloading/installation.
This could bring about an easier way for users to browse/install new applications over the existing built-in app directory.
See http://magnet-uri.sourceforge.net/ for more information on the Magnet URI scheme.