LiveJournal users will want to take a look at LiveJournal AddOns, a free extension that provides access to LiveJournal services from the Firefox interface. It notifies you when you've got a new message or comment, when friends update their pages, or even when friends' birthdays approach. It also adds extras like built-in forms, style management, quick access to last entries, and quick text inserts. You need a LiveJournal account to use it, but they're free, though premium services are available, too.
We installed LiveJournal AddOns and restarted Firefox. LiveJournal AddOns placed a series of icons in the add-ons toolbar on the far lower-right edge of our Firefox interface: Friends, Inbox, Comments, Birthdays, and Journal, with counters displaying new entries for the first three. We clicked the Journal control, a pencil icon, and signed in to LiveJournal. The icons became active with our account, changing color as they did so. Next we clicked Tools/Add-ons and opened the extension's options. These are fairly numerous, beginning with fields in which to enter URLs for our journal and friends pages, including an option to check groups. Aside from Import, Export, and Reset controls, most of the other settings are check boxes for things like floating icons and tags. Using LiveJournal in Firefox is easy with LiveJournal AddOns' controls. We didn't even need to open a page to see what was new; hovering the cursor over any of the icons called up a small pop-up with the latest data for the service. Clicking any icon opened the service in a browser tab. We clicked the head icon, and our Friends page opened; clicking the mail icon opened our Inbox. Right-clicking any of the icons called up extensive context menus, including access to the Settings dialog. We could even open multiple Journal pages.
LiveJournal AddOns made it very easy to access LiveJournal from Firefox. It might take you a while to get everything set up just the way you like it, but that's because LiveJournal AddOns has so many ways to customize how and what it does. If you use Firefox and LiveJournal, it's extremely useful.