Linux only: The smoked glass, Mac-like notification alerts are one of Ubuntu 9.04's best features, but they're not yet compatible with every program, including Firefox. An experimental extension can fix that, moving download notifications into Jaunty Jackalope's pop-ups.
That's all FirefoxNotify does, really, but for Ubuntu users looking to give their desktop a more seamless look and feel, it's a nice fix. The add-on itself is only 9K or so, and while it's technically unofficial and not thoroughly tested by Mozilla's team, it seems to work just fine for its single purpose. Until our tipster pointed it out, I was pretty happy to stick with Lifehacker favourite Download Statusbar, but this might just tempt me to switch. If you're a Mac user looking for the same kind of Growl download notices, try the previously mentioned Growl Notifications add-on.