Agaricus Bisporus is indeed universally safe, and comes in large, small, brown and white varieties. The variety of flavors and textures that awaits the slightly more adventurous is a delight!
There are also other tasty cultivated mushrooms like shiitake! More expensive (at least in the US), but much cheaper than a visit to the emergency room after eating a dangerous wild mushroom...
"Any wild mushroom can be eaten - once."
I limit my foraging to the mushroom section of the grocery store.