When I upgraded to Ubuntu 11.04 it forced removal of "prism" which I had been using to make local executables of on-line web applications. During the Synaptic based upgrade to the latest Firefox I also lost the add-on that allowed Firefox to make locally executable applications from on-line web URLs.
Not wanting to back-port prism, and not wanting to go back to an older version of Firefox I decided to see of there was some other way to make web-based applications become click-able applications via my local menu.
Turns out that it is fairly easy. Using the browser, go to your desired web based application page and copy it's URL by highlighting the URL and hitting CTRL-c. Then open the menu editor at /System/Preferences/Main_Menu. Select the base menu where you want your new application to be listed, and open a "New" menu item at that level. In the "Command" section enter firefox, followed by a space and then use CTRL-v to enter the URL that you just copied from it's web page.
Then clean up with niceties like a descriptive name for your new application and a longer description of what it does. Save this new menu entry and you now have your own web-based application that can be executed by clicking on it as an entry in the Applications menu.
This is essentially the same as what was previously done using prism or the remote application tool of older Firefox versions. Difference is that now you are in control of how it works and can build your own versions of particular on-line applications whenever and however you want to do it.