LIBCRYPT  I hate to say it, but there's no ad-blocking proxy out there that won't significantly slow down browsing. After a few months of GlimmerBlocker, I've had to switch back to Safari Adblock. Pages now load far, far more quickly.  
(Version 1.4.2)

TH3 J0K3R  Still THE BEST

seems like it speeds up web browsing cause your not forced to waste bandwith on ads  
(Version 1.4.2)

CORPSECORPS  After using Privoxy for a periods of time in the past, i thought a proxy would be a good way to go if it just wasn't as horribly user unfriendly as that software.

This still isn't very user friendly: i.e. no simple interface for immediate changes to ad blocking.

The only really good solution i've found for ad blocking is Firefox + Adlbock Plus with Element Hiding Helper.

I had to toss GlimmerBlocker, because as a proxy it necessarily affects all browsers and i don't need the chaos of both GlimmerBlocker and Adblock Plus working in tandem. Back to an ad-storm while using Safari and other browsers.  
(Version 1.4.2)

FLUENTNUDGE  Apparently Glimmerblock bypasses Little Snitch which allows _any_ app to connect if they use the proxy... Unless you approve each and every connect glimmerblocker does...

So uninstalled...  
(Version 1.4.2)

DREAMKATCHA  Yes, it blocks ads, but unfortunately that's not all it blocks. With this enabled, half the pages I (try to) visit need to be refreshed before they'll appear, and the ones that do load first time take three times as long. I'd rather see the ads than go back to dial-up speeds, thanks.

I tried to uninstall it as per the instructions and the 'activate GlimmerBlocker' checkbox was greyed out so I had to delete the preference pane and then re-install it just to see if GlimmerBlocker was the cause of my problems. It was.  
(Version 1.4.2)

PROGRAMHAPPY  It is not blocking any ads from googlesyndication.com or doubleclick.net. It may not be working altogether.

OS 10.6.1 & Safari 4.0.3  
(Version 1.4.1)

IVANOVITCH  I'd be more impressed if it didn't block Facebook:

"Request failed.

Got java.io.EOFException (Unexpected end of ZLIB input stream): http://www.facebook.com/n/?reqs.php&mid=1.....(etc)"

Oh well...  
(Version 1.4.1)

JOSHP  If you remove this prefpane, iTunes can't get to the iTunes Music Store or update podcasts until you also remove the proxy info from Safari. Go to Safari--> Preferences--> Advanced--> Change Settings and uncheck Web Proxy.  
(Version 1.4.1)

RONL  I was using Glimmerblocker, but because it uses a proxy server it increases the overhead for Safari and consequently Safari was sometimes hanging when loading pages.

Now I use a userContent.css style sheet for Safari instead of Glimmerblocker.

Safari works faster this way and only takes a minute to set up... and of course it is free.

Both Safari and Firefox can easily use userContent style sheets via their Preference settings.

In Safari simply go to Preferences > Advanced > Style sheet... and select your userContent.css

You can find the latest css at: http://www.floppymoose.com (or if MacUpdate deletes this URL do a search using Google for "Better Ad Blocking for Firefox, Mozilla, Camino, and Safari").  
(Version 1.4.1)

ROBOTANK  The transition to Snow Leopard highlighted for me the substantial advantage Glimmer Blocker has over other Safari ad blockers. While all Input Manager based plugins stopped working with 64-bit Safari, Glimmer Blocker continued to function without a hiccup. While I unfortunately had/have to wait for a couple other plugins to be updated, at least I didn't have to deal with ads. As for Glimmer Blocker having a less thorough filter set than Safari AdBlock, I've found that with some of the additional filters linked to on the GB web page installed, I've managed to get nearly complete ad blocking, so far only needing three domains on my own filter. Also, I've found that Safari's page loading speed with GB is far superior than with AdBlock. I suspect this has to do with the way ads are blocked, though I could be wrong. It looks to me like AdBlock loads the data from the ad server then prevents it from being displayed, while GB prevents the data from being loaded at all. In any case, I'm very pleased with GB, and I strongly recommend it over the existing alternatives.  
(Version 1.4)