This tip could work for any streaming music service. In Firefox.

• Add a bookmark for www.slacker.com
• n the Bookmarks Menu and right-click on the bookmark. 
• Choose the Properties option.
• Now check the box that says Load this bookmark in the sidebar.

The next time you open that bookmark it will pop-up in the sidebar

Now when you click on your bookmark you will notice slacker loads in your sidebar..Awsome humm but you will notice when you close the sidebar your music stops kinda defeats the purpose if you ask me. There is an add-on for Firefox that will help this. Let get All-in-on-Sidebar, Install and restart Firefox. Now you can click the bookmark you made. Try closing the sidebar while your is still music in your side bar reopen to skip forward etc..