Sleep Like the Dead should be your first stop. They provide in-depth reviews, discussions and ratings of every kind of sleep-related product, including mattresses, sleeping pills, electric blankets, white-noise machines and insomnia treatments. There are tips and tricks for shopping, including how to return products.
Something that may especially pique the interest of my romantically married readers is the comparison of mattress types and sex suitability, based on data from actual mattress owners. They considered attributes such as bounciness and noise level. The data, just like everything else on this website, has been thoroughly analyzed, explained, and put into pie charts. The results just might surprise you.