I too have heard spider plants to be the best.

An agave wont get enough sun light in the house. It would be hard to keep inside.

JoJo

It may have been Cycad actually, not agave.

I've heard Sansevierias are very good as well, and tolerant of low light.

In my plant book there are a list of all different kinds of plants. These are the best of the best it says. Boston ferns, Florist mums, Pygmy date plum, 'Janet Craig' dracaena, Rubber plant, English ivy, weeping fig, Peace lily, Area palm, Corn plant'Kimberley Queen' fern, & Bamboo palm. I hope this list helps a little.

Sansevieria do have the best reputation to use for this purpose, and take next to no care. Wonderful house plants and many species to choose from. Norma

I heard spider plants were great for that. (But im not an expert)

Here's a great list of plants from a study done by NASA...
http://en.wikipedia.org/wiki/List_of_air-filtering_soil_and_plants

But when it comes right down to it, I wouldn't expect one houseplant to make a noticeable difference in air quality.

Found this link while surfing the web today if anyone is interested.

Tina

Here is a link that might be useful: Air Cleaning Plants

Check out the book How to Grow Fresh Air by B.C. Wolverton

dirtslinger2, here is a site which might help.

http://www.zone10.com/nasa-study-house-plants-clean-air.html