Stylebot
This is a fantastic extension for Chrome. This lets you easily edit the styles of a web page, and have them be saved and applied next time you visit.
The demo shows one excellent use: improving a site you frequent. I did that for Kotaku/Lifehacker. I never use the Share box, and always mistake it for a search box. So, share box hidden, search box moved into place.
Also, I have refrained from Adblockers in the past because I don’t want to block all ads. I respect websites’ needs to make money. But I don’t respect the need to make a website that is more about the ads than the content. So, certain websites that cover their articles in flash ads, or have far too many ads in the sidebar, have their ads hidden.
Yes, I know. Shame on me, etc.