There is a secret place on Ravelry where you can enter codes that alter the site's features. We use this when testing new things that are still in development but it also contains ideas that were never finished and small preferences that were never made official. It's a little like the "labs" section in Gmail's settings, if you have ever tried that.
To use a code, visit http://ravelry.com/swatch and enter the code. If you want to stop using one, you can go back to that page and turn it off. Make sure to bookmark the page for later!
If you are game, here are a few that you can try. Most of these have been around for many many years and never graduated to become part of the real site.
NOTEBOOKMENU
Alternative menu on the 'My Notebook' tabSTICKYHEADER
Make the site header stick as you scroll. I think this one might be quirky.LARGEFONT
Enlarge the base font that is used on RavelryLIVEFORUMS
Update parts of the forum and group pages live (post counts, reply counts)RESPONSIVE
Allow mobile views on non-mobile devices (by narrowing your browser)DROPBOX
"Save to Dropbox" option on pattern receipt pagesNOMAIL
Show "no new messages" in the upper right corner when you have no new unread messagesALLBRAN
Changes the tagline on the front pagePORRIDGE
Changes the tagline on the front page (Canadian/British English)BACON
adds a big piece of bacon. Some people have had this one turned on for years!? To each their own :)