Where you are a member of multiple organizations, you can switch organizations using the link in the account panel dropdown.
1) Click the drop down box to view your settings.
2) Click on Switch To to show all the organizations you belong to.
3) Select the organization you want to change to.
The only organizations shown are ones that you have already logged into in this browser. If there are organizations you belong to that aren't listed in the Switch To list, you will need to navigate directly to that organization and log in first. Then they will appear in the organization switcher.