As I have updated to the Ubuntu 8.04 I now have firefox 3.0 Beta 5 installed on my computer. Some of my extensions where not updated for Firefox 3.0 but I have found some betas of these extensions or replacements. Here are the extensions I've found: I hope these links can be useful to someone else.

• Firebug - Use the 1.2 beta version which could be fetched on firebug's website
• Del.icio.us bookmarks - Use the beta provided on del.icio.us blog
• Document map - This extension shows the document headings as a tree: this is really handy when reading huge pages. This extension has no version for Firefox 3.0 beta 5 but I have found another experimental extension doing the same job: HeadingsMap (es).

Now I can use Firefox 3.0 like I was using Firefox 2.x...