Your recommended OSX tweaks and Apps?

OSX is a wonderful OS to begin with, but for me what really sets it alight are some really great Apps and tweaks which help make the OS more a more personal, streamlined experience.

Here are some great tweaks and Apps I've found, I would hope that more people can add to this post and we have a repository of sorts here.

Growl

Growl-notifications_medium

Paul Miller once called Growl one of the greatest innovations to personal computing and though I think he was possibly slightly high when he stated that, it's definitely a must for streamlining incoming notifications. Basically it can be customized to be the display of notifications for many programs instead of their standard notification system. Also there will be a floating notification pane on your screen if there were incoming notifications while you were away from the system.

Alfred

Alfred3_medium

Alfred (it was featured here today) is a glorious Spotlight replacement for Mac. It's really customisable in what you allow to be searchable, allowing files, folders, facebook, gmail, apps, whatever. The big hitter is that it seems to be quicker than spotlight, though this is probably due to only displaying about 1/5th of the actual results. But really, who ever uses a result half way down the Spotlight list? Also included are system commands.

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I've a few more to add, but no time right now, add yours!