I've been using a Chrome extension called Ghostery for the last couple of weeks and I just wanted to write a quick review on my thoughts so far.
Ghostery (apparently there's also extensions/add-ons for Firefox, Safari and IE too) is a cool little app that runs in the background of your browser and detects trackers on the web pages you're running. These bugs track hits on pages, and advertisers use them to target ads at you (by keeping track of what sites you visit). There are plenty of other extensions that allow you to block these completely - FlashBlock, AdBlock, etc - however I don't think that this is entirely healthy for the free web. Advertisers keep all of the important sites on the web afloat - Google, Facebook, most (commercial) blogs, etc - and I don't want to block their revenue stream entirely.
Ghostery allows me to check to see who is monitoring my visits and how many bugs are embedded on a page. It does also allow you to block bugs if you like, and you can click through to see their privacy policies on each one. I much prefer this method as it allows surgical blocking - I want to allow sites to use Google Analytics, but not let a certain advertiser track me.
What I'd like Ghostery to do next though is allow users to rate each tracker, perhaps with a 5 star system. This way I don't have to look up every tracker to see if they're legitimate. But, all in all, a nice little (it's very lightweight - I've not noticed any slow down at all) extension.
