Watch this screencast. It is good. At least I learn the hot-key to switch tab in Firefox is "Ctrl + Tab".
All software mentioned in this screencast is somehow need money. I like Writeroom, but 2.0 is a shareware with a price tag of US$ 20. Desktopsweeper is a donationware.
I think the real poorman distraction free desktop is
Well, it is a little bit of poseur-ism.* But terminal with vi is a very promising replacement of Writeroom. If you want to learn some vi, type "vimtutor" in terminal. You can use "nano" as your text editor if you feel vi is too hard to learn.
* poseur, according to wikipedia, is "a person who adopts the dress, speech, and/or mannerisms of a particular group or subculture, generally for attaining acceptability within the group. " It is usually used in punk, heavymetal or emo scene. I think there are some UNIX poseurs in HK. If you ask them about UNIX, they will go on and on about how cool it is, while giving little or no background about it. For UNIX poseur, they will talk about why Linux is not Unix all day long, why Unix is better than Windows or Mac OS while no insight on how to use them. They will not talk about how to use UNIX to acomplish common task (because they don't know) They jumped into the bandwagon of UNIX because it is a sign of geekiness. I think I am a UNIX poseur too. The only UNIX god I know is Albert MC Tam a.k.a. al-beer. He is a specialist, as written in his name card.
p.s. Using a modern-day iBook G3 700MHz for vi is a sort-of "A-bombing the flies". How pro it is.
p.s. To be exact, I am using VIM instead of vi. In Mac OS X, when you type vi, it will mapped to VIM. In Linux, when you type vi, it will mapped to VIM in vi emulation mode. It is not easy to use and very 80s. (e.g. It will not prompt you if you have been changed to "insert mode")