Blackout blinds are great for rooms where you want, or need, to be able to block out the light. Once installed, they do a very good job of keeping a room in almost total darkness even during the daytime. While they are slightly more expensive than regular blinds, many are still quite reasonably priced, especially roller blackout blinds.
Parents of young children find them very useful if their child still needs to nap during the daytime but has trouble doing so due to the room being too light. They are also very helpful during summer, when a very early sunrise may wake up your child. Other practical uses include hanging them in rooms where you have an operational home theater and need total darkness. They have also proved very useful to families where someone works shift-work and needs to rest during the day.
You can find many different styles of blackout blinds. Roller blinds are perhaps the cheapest and the easiest to install. They can even be installed behind other window treatments, such as curtains, in any room where you are concerned about your window furnishing appearance. This works well in a living room that also doubles as a home theater. You may not want to only hang roller blinds in your windows, but you should be able to hang blackout roller blinds in such a way that the curtain actually hides them from view when rolled up.
Other types of blinds, such as Roman blinds or bamboo blinds are also available with blackout backing. These type of blinds may be better for a room where they are the only window covering as they look great yet still provide you with the option of total darkness in a room should you need it.
Blackout curtains can work well also. These are often regular curtains that are backed with a blackout material. You do need to allow extra overhang on the sides for them to be totally effective but if hung properly they will provide you with a way to completely block out most of the light from a room when needed.