Great news for Safari 5 users! A new extension called NinjaKit lets you install greasemonkey scripts (such as FB Purity).

Its a much simpler process to install than Greasekit as it doesnt require SIMBL, the extension is self contained and is also PC + Mac compatible, once you have installed Ninjakit you can then click on any greasemonkey script link to install them.

The extensions home page is here: http://d.hatena.ne.jp/os0x/20100612/1276330696
and heres an english translation, for those of us who dont speak japanese.
To install NinjaKit you just need to click the “Safari for NinjaKit” link (Please note the extension link wont work in the translated page, you need to click it in the original page)
Once you’ve installed that you can then install any greasemonkey script you like, of course not all will be compatible but a lot should be.

It works great with Fluff Busting Purity, I also successfully tested it with two of my Flickr scripts : Multi Group Sender and Flickr PM.

You can install the latest version of FB Purity (v3.11) here: http://www.fbpurity.com/install.htm