OS X Lion: If you like how Lion's new scroll bars disappear when not in use, but want to get them back in some applications, LionScrollBars is a tool where you can set the scrollbar behaviour for each app.
We've highlighted ways to remove the scroll bars completely in the past, but if you want more control, LionScrollBars is a great tool. Each app in your Applications folder shows up in LionScrollBars with four options: system default, automatically, when scrolling and always. You can set each app independently of the system default so you can control the behaviour for apps you read large articles in, or if you simply like having the scroll bar in certain places but not others. It's a free download from MacUpdate.