Chrome now has Extensions. Similar to Firefox add-ons, Chrome extensions are small widgets that sit on your toolbar and extend the functionality of your browser. There are hundreds of extensions currently available for Chrome, including a Gmail notifier, ad blocker, Google Wave notifier, ChromeMilk (Remember the Milk widget), and Chromed Bird (the Chrome equivalent of Echofon, aka TwitterFox).

https://chrome.google.com/extensions?hl=en-US