Can I use the Chrome Web Store in Chromium? Or do I have to install Chrome for that.
You can access the Chrome Web Store here : http://chrome.google.com/webstore . But if you want to install the apps, you have to get Chrome/ium 8 or greater. Their icons will show up on the "New tab" page.
The web store just redirects to https://chrome.google.com/extensions currently. I don't have Chromium installed to test, but presume you can install these extensions.