The first solution came during yesterday's night. Use a blogging platform and add a new blog entry for each bookmark, with tags associated ... That might seem a bit "overkill" but it has several advantages that I will detail further.

The second solution is, of course, the DIY solution. But I've been thinking of a specific one I would do. It's not necessarily the one best suited for this task but it would involve some technologies I'd like to work out.
It would be a quite simple xml file, one entry per bookmark, with a <taglist> containing the tags, a <state> tag to mark it as read or unread (very often I keep some bookmarks to read them later, and very often I forget to do so :-/ ), probably another one to know if it's a personal bookmark or a professional bookmark (to be able to keep both at the same place, but separated), a field to keep the date and probably one for a title and a last one for a description (which will mostly remain empty as I am to lazzy to fill it :).

Why use an xml file and not a database backend ?
Well, because there are several xml technologies I'd like to test or to reuse. The first one is the RelaxNG schema language. I've already used XSD schemas several times and I've read everywhere that RelaxNG is much simpler to use but does the task as well, so I want to give it a try.
The second one is xslt ... I've already used xslt but I want to continue using it and improve my skills. I would use xslt to build a complete set of pages from my xml bookmark files with corresponding queries when I select a set of tags, counts for each tags, etc etc ...
The third one, linked to the previous point, is I would like to minimize the use of a script language. And if possible, use python instead of php ... I'm not really fond of php but I'll use it if I have to. I would only use the script language to build a small interface for adding a new bookmark ... or maybe, why not, provide a webservice to do so ? With a nice WSDL file :)


Well, now, let's see the pros and the cons of each solution :

Blog Solution :
+ easy to set up and get it working
+ search integrated (by date, etc etc ...)
- is it possible to get the blog entries combining several tags ? (let's say I have a link tagged with java and "webservice", can I retrieve it by combining those two tags or do I need to browse through all links tagged as "java" or all links tagged as "webservice" ?). It mainly depends on the blog engine but does one with my requirements exist ?
- Need of a manual synchronization with your web browser (or maybe possible with an extension and the xmlrpc interface of the blog ? (I think dotclear and wordpress, at least, have one)

DIY XML Solution :
+ Will fit all my needs
+ Make me work different technologies
+ Possibility to make a firefox extension to synchronize with the firefox bookmark manager ? (maybe by tweaking some existing extension that let you upload on your ftp your bookmarks ?).
- Take time

So, it's still needs some thoughts and maybe some pieces of advice from friends ? :)