SIMBL (pronounced like “symbol”) is software for OS X that makes plug-ins possible in places where they wouldn’t normally be. Following are four extremely useful SIMBL plug-ins that I use: (See below for installation help.)
Megazoomer allows you to make just about any open window fullscreen. This is a very convenient if you want all of your focus on a particular document your working on, or if you want to browse the web with as big of a window as possible.
Afloat provides you with even more control over your windows. You can easily change the transparency of a window, make it stay above all other windows, pin it to the desktop, and do many other useful things with it.
Keywurl is a Safari plug-in that lets you define shortcuts you can type in the address bar. For example, you could put “wiki OS X” in the address bar to quickly go to the Wikipedia page on Mac OS X.
SafariStand is a multipurpose plug-in for Safari, which when installed is accessible through a “Stand” menu. SafariStand has too many features to list, but they cover everything from letting you preview your tabs in a sidebar to automatically changing the font size of certain sites to letting you download a flash video by command-clicking it.
Two of these plug-ins, Afloat and Keywurl, come with SIMBL included, which needs to be installed before any plug-ins will work. If you want to install a plug-in that does not come with SIMBL, and you haven’t installed it before, you need to download SIMBL here first.
Some SIMBL plug-ins (like Afloat) come with an installer to install themselves, but sometimes you will end up with just the plug-in, identifiable by its .bundle extension, and need to know where to put it. To install a plug-in, open Library?Application Support from your home folder, then create a folder named “SIMBL” and another folder inside SIMBL called “Plugins” (assuming those folders don’t already exist). Finally, you just need to drag the plug-in into the Plugins folder. Running applications won’t be affected by a newly installed plug-in until you close them and reopen them.