Using anchors as a way to let users bookmark various dynamic effects about a page:

ad-hoc

• tips on using document.location.has
  • quick way to check for single flags
  • don't use it -- it has a bug in Firefox
• [stackoverflow] How do I modify document.location.hash without making the page scroll?

plugins

• Ben Alman's jQuery BBQ
• jQuery.observeHashChange.js
• more