What's the deal with Americans? If there's some kind of behavior that's bad for the environment, we seem to always be its biggest fans. We drive the most, eat the most meat, buy the most stuff, build the most sprawl - and buy the softest toilet paper.
As far as I can tell, toilet paper made from recycled paper works just as well, but it doesn't have that soft feel that Americans apparently require. For that you have to cut down trees, including old-growth forests in Canada. So recycled-content toilet paper is a miniscule part of the American market, unlike in Europe and Latin America where it accounts for about 1/5 of sales.
According to Greenpeace, these are the brands best for the environment (the first number is percentage of recycled post-consumer waste, the second is overall recycled content. All avoid chlorine bleaching):
Green Forest 90 100
365 80 100
April Soft 80 100
Earth Friendly 80 100
Fiesta and Fiesta Green 80 100
Natural Value 80 100
Seventh Generation 80 100
Trader Joe’s 80 100
It's far more important, of course, to reduce/eliminate your driving and meat eating, buy less stuff, weatherize your home and switch your lightbulbs, etc. But if you can help save a tree you might as well.