gnash
I’ve not exactly seen much working with Gnash, which is what I have installed: gnash and gnash-plugin. A quick visit to Youtube, confirms that gnash is still not exactly usable, and the bug seems to be with ActionExtend and Super (AS inheritance) not being implemented yet. There is hope nonetheless, as Lulu TV also use these features, and are hosting the Gnash developers wiki, which might mean there’s some corporate backing of gnash development.
gnome-dictionary
gnome-utils provides the Dictionary, which is just a front-end to an online dictionary. This is great, but works horribly if you’re offline. Mac OS X clearly has the upside here, as I can just use the Dashboard dictionary applet to find words. It also comes with a working thesaurus, something the “Similar Words” feature in the GNOME Dictionary doesn’t seem to grok.
Deskbar
Like Quicksilver? You’ll definitely like the Deskbar Applet (deskbar-applet from Fedora Extras). Its not Ctrl+Space controlled, which it instead has picked up on Alt+F3 as the keyboard shortcut of choice. It has Beagle (Spotlight equivalent) integration, can connect to the Fedora bugzilla just via a bug number, and do so much more. I don’t have Thunderbird integration, and notice that its a planned feature for the future – I can’t hardly wait.