I currently have my own bookmarks application (cakemarks) written in PHP running on my server. However, I am considering to just import all those bookmarks into Firefox.
The cakemarks project was started by me to have my bookmarks across all browsers and all devices. Since they live on a server, there is no need to sync, and I could use any browser I want. However, even on the impressive hexacore Opteron with 16 GB of RAM, this is painfully slow (it takes more than 500 ms to generate each page). Adding bookmarks cannot be done right in the browser, but has to be done through a bookmarklet and so on. By moving them back into my primary browser, I expect a big usability improvement, although I will use the ubiquity.
Now regarding the how: I know that Firefox supports to import and export bookmarks via HTML, but I am not sure whether I should just create an export which creates something like Firefox exports, or whether there is some better way.