GlimmerBlocker is an open source OS X preference pane for 10.5+ (they’ve just released an updated version that should work for 10.7)
It serves as a proxy that allows you to block sites/ip address, and to inject code. I use it to run userscripts (as in GreaseMonkey, GreaseKit, etc) such as Helvetireader2 to make Google Reader more friendly. I run it through GlimmerBlocker so I don’t have to install the script in all my browsers; I run OmniWeb, Firefox, Safari, Opera, and Chrome (I used to run Camino but haven’t had a chance to reinstall after an unfortunate incident)—each rock in their own way, I use each for certain kinds of work and for testing.
I’m sure I’ve posted about it before, but I’m posting it again because the developer(s) are so damn cool. The OS X 10.7 compatible release included a slight annoyance, it still worked but was…slightly annoying.
I emailed the developer(s) and by the time I got through with a game of dominos with my dad I had an email from Peter containing a new version!
I lost both games (dad’s been playing for 70 years!), but at least I had good news in my inbox to mitigate the defeat.
So, Peter, if you ever see this—Thanks!