A few years ago, we had to replace our mattress. I really wanted to avoid springs because they were a major source of discomfort in every mattress I had ever had. However, conventional foam mattresses are pretty terrible for the environment and super expensive.
In researching various companies, we came across Amerisleep, which eschews petroleum based materials for plant-based materials (soy oils specifically), cleaner manufacturing (details on their website and in various consumer review sites), and uses minimal packaging. Their mattresses also cost a heck of a lot less than Tempur-pedics and, based on reviews and now my personal experience, don't get nearly at hot as other foam mattresses.
We bought a Queen sized "Revere" (the medium-firm option) on a deep discount (they do weekly/daily deals) and they included their box-spring for free, and we couldn't be happier with the set The mattress came rolled up in a carboard tube and plastic that was easy to remove, the mattress didn't require any de-gassing, and the box spring/base took minutes to assemble. The mattress still feels new and keeps us comfortable, which is a feat since Adam and I have different sleep styles and Adam has a dodgy back.