UPDATE: Along with Firefox (as always), Xmarks is available for Chrome, IE, and Safari.
Status (as of Oct 14, 2009):
Chrome – open alpha
IE – full support
Safari – full support

Other possible uses

• Family Computers: If your like my family and every member has their own computer, you may find it useful to synchronize everyone’s bookmarks. Since I don’t have a printer hooked up locally to my computer, I am constantly using my siblings computer for all of my print-jobs. Xmarks has a feature that really makes this interesting. The feature  I’m taking about is the use of profiles. In the example of family computers, you could create individual profiles for everyone, that way when they go to any computer, they just change Xmarks to use their profile and instantly they have their bookmarks loaded.
• Password Sync: Along with syncing your bookmarks, the add-on can sync your saved passwords securely between your systems.
• Project Collaboration: Sync a folder of bookmarks between your project members, that way they’re constantly on your computer. This practice can save you time by keeping you from having to look through chat logs, trying to find that one stupid link. (btw, the instant messenger Gtalk has a great chat log search feature)

If you think Xmarks is an add-on that you would like to try out, you can find it @

https://addons.mozilla.org/en-US/firefox/addon/2410

Here’s the Xmark site (cloud):

https://my.xmarks.com/

Comments are welcome!

• Interface: Very simple and easy to setup. It initially shows up on the status bar at the bottom of the Firefox window, but after glancing at the settings, I discovered that you can place it on several other parts of the window. I chose the bookmark bar, simply because I like everything to be at the top of my screen.
• Information Displayed: You can add several different stations to Weather Watcher. I added two stations that are both within 5 miles of my house, one at the local high school and the other at the municipal air port. All of the icons display information when you hover over them with your mouse. The globe icon displays the current Doppler image. The other icons/the weather status icons display the forecast information. You can change the update time for all the information. I currently have mine set to 3 minute updates.
• Why did I choose this? Weather Watcher Live has a very simple and easy to understand interface with a good amount of customization. Highly Recommended!

Chatzilla

• I dont have too much to write about this, but as far as I can see, it’s basically a simple replacement for having a full time IRC application, like mIRC. Basically from what I can see, if you’re not big into IRC chatting and you don’t feel the need to have your own dedicated app, this is a good choice for you. A lot of software developers use IRC chat rooms as a means for supporting their users. If you’re like me and you download lots of different applications, this is good for you, so you can just click on the IRC support channel link and the chat room will open immediately.
• Why did I choose this? Chatzilla is by-far the most supported and downloaded IRC add-on. It allows a good deal of color and font modification to the chat windows. Recommended for the IRC novice, but not a replacement for mIRC or any other dedicated IRC application.