Usefull plants

I remember being taught in primary school that plants convert carbon-dioxide (CO2) into oxygen (O2), and because of this is very usefull to us.
About a month ago, I decided to add more 'green' to my cubicle at my office, hoping that any beneficial affect, such as air purification, these plants could have at my office could help my day to day work.
On this line of thought, I just saw this video on TED on exactly that topic, which plants are good for cleaning the air.
Most interesting to note is the Mother-In-Law's Tongue (Sanseviera trifasciata), which apparently does the CO2-O2 conversion during the night, thereby making it an ideal bedroom plant. I will be getting me a few of these for my bedroom in the near future.