twine is software that allows you to create interactive fiction quickly and easily!

it runs in both windows and mac. i have created a few stories in it and it makes the process easy and fun! here is a screenshot of the interface for twine: 

here is documentation on using the program itself  and here is a forum where people post about it!

as for games made in twine, here are a few examples:

• roadside, north south east west, and pissed (all made by me)
• howling dogs
• the sky in the room
• afternoon in the house of secrets
• a large post of twine games