Below are my top 3 Chrome/Chromium extensions. All are .crx files, meaning one click install, and need the most up-to-date dev version of Chrome/Chromium and require that –enable-extensions is added to the launcher. Download links are provided.
1. AdSweep Adblocker
Does what you think it does: Blocks ads. I find it to be very efficient and pretty much any and every advert on sites i visit. What also makes it great is that it doesn’t just block the ad, it removes the frame where the ad would be – so you don’t get whacking great bit white blobs dotted all over a web page! Nice!
2. GMail Checker
GMail chcker sits in the Chrome taskbar and tells you how many unread mails you have. It constantly refreshes itself so you can be sure that you’re not missing out on an important e-mail! Clicking on the notifier takes you straight to your inbox.
As the Chrome extension framework matures, it’d be nice to have options to set the refresh rate as well as perhaps implementing some form of ‘jump list’ when right-clicking on the notifier that gives you options such as ‘Compose’ or ‘Refresh.’
You can also get a similar extension for HotMail.
(Mini version: http://dl.getdropbox.com/u/1703837/mini.crx)
3. Google Reader Notifier
Following the same premise as the Gmail extension, Google Reader Notifier tells you how many unread articles you have in Google Reader. Clicking it takes you to the Google Reader homepage.
Others
A few others that are coming along nicely include a facebook notification extension that does for facebook what the Gmail and Reader tools do above and a slightly-not-quite-perfect weather add-on that sits in your status bar and, you guessed it, tells you the weather.
As always, do keep in mind that these extensions are still in-progress given the Chrome Extension framework is still being improved all the time.