Here's a small demonstration of the OAuth library for JavaScript. You can fill out a form to get a request token. Then copy and paste the token into the form to authorize your consumer. Then copy and paste the token and secret into the form to get an access token. Then copy and paste the access token and secret into the form to echo a message.

When using Microsoft Internet Explorer, you can prevent annoying warnings about protecting your security by going to 'Tools > Internet Options ... > Advanced > Security' and checking the box 'Allow active content to run in files on my computer'.