A useful trick to make a great use of custom fields outside of the loop, in your sidebar for example!
Quick tip that will allow you to insert an internal or external URL in a custom field for a page, and when a user visits that page, they will be redirected to the URL you put in the custom field.
And another taxonomy plugin available! I let you have a look at both Justin Tadlock's and Yoast's, and let me know which one is the best in your opinion.
It seems Justin's one is a bit more advanced though.