One of the largest auction websites, eBay enables you to search for, purchase or sell virtually anything. Adding eBay to your browser's toolbar enables you to shop from eBay no matter where you are on the Internet. You can find your favorite products, and receive alerts to help you win more of the items that you are bidding on.
Instructions:
1) Download the eBay toolbar. Go to the eBay download page and click "Download Now".
2) Click "Save" to launch the file-saving dialog box. From the "Save in" box, select the desktop then click "Save" to download the eBay toolbar installation file on your desktop.
3) Double-click the eBay installation file, then click "Run" to launch the installation wizard. Click "I agree" after reading the terms and conditions. The setup wizard installs the toolbar. Close and relaunch your Web browser. You should see the eBay toolbar on your browser's toolbar.
4) Alternatively, add a specific eBay tool such as eBay Motors, or eBay Italia, to the Google toolbar on your browser. Go to the Google Toolbar Button Gallery page and click "Add to Toolbar" next to the eBay tool you want to add to your browser.
Source - eHow