I've posted a new test release of Firefox Portable for folks to try out. There are a few new changes. The most interesting is a new feature:
Mime-Types Processing - The launcher now adjusts the paths within Firefox's mimetypes.rdf file in your profile. What does this mean for you? It means you can specify which portable apps open which types of files in Firefox Portable and it will remember them even as you switch computers. So, you can specify Sumatra PDF Portable as the opener for PDF files or OpenOffice.org Portable as the opener for DOC and XLS files. You can find these settings in Tools - Options - Content - Manage. Just select the file type you want to use and select Change Action and then tell it to "Open them with this application". (If the extension you're interested in isn't there yet, just click a link to a file of that type in the browser and take it from there.) It will work for any apps within your PortableApps directory.
Also, a few settings changes: form filling, download history and browsing history are now enabled by default.
Please give it a try and post any feedback:
Download Mozilla Firefox, Portable Edition 184.108.40.206 Pre-Release