First, congratulate on the launch of PortableApps.com.
What you have done here will make the life of many people easier.
You should be proud of your work .
Ok, back to the topic, Firefox, Thunderbird, and OpenOffice.org are the major pillars of open source apps that benefit millions of people. Another application I bet most of us would like to see is Portable GIMP (or Portable GIMPShop). I used GIMP at home under Linux and would like to do so in my workplace without any installation so my system admin would not complain.
GIMP has been criticized for its arcane interface, and that's why GIMPShop was created to modify its interface to follow the menu layout of Photoshop, so that Photoshop users can use GIMPShop right away with ease.
If you can make GIMPShop portable, I am sure the response will be as overwhelming as Portable Firefox. For one thing, you will help marketing GIMPShop to a lot more people as a right-away usable Photoshop alternatives without any installation hassles or troubles.
Thank you for your great work, John. Keep it up!
(Btw, Paypal is not working atm)