Twitter Bootstrap Button Groups

Button Groups from Twitter's Bootstrap framework. You can basically build these with a or button elements and use them to join multiple buttons into one single component.

The official documentation mentions some best practices -

Always use the same element in a single button group, a or button.
Don't mix buttons of different colors in the same button group. This basically means, don't mix btn-primary and btn-success (for example) in the same group.
Use icons in addition to or instead of text, but be sure to include alt and title text where appropriate.
Button groups with dropdowns should be called out separately and always include a dropdown caret to indicate intended behavior.

In the button group you can also use radio buttons where only one button can be put into the active state or checkboxes where multiple buttons can undergo the active state. Although this requires Javascript.