I recently ordered a memory foam bed online. It arrived in three boxes and had to be put together. The foam mattress was easy to put together and came with a memory foam pillow. It took a bit of time for the pieces to expand but then they were just stackable and the cover held them together. It is very comfortable and convenient is it is light and easier to move than traditional mattresses.
I put it on a futon frame and it fit fine but is probably best on a normal frame bed. I was very impressed with how comfortable it is. I always worried they looked like they would be to warm in summer but it is no more warm or cool than other mattresses. You seriously need to avoid getting it wet though because it if you do it can take forever to dry out so cleaning can be difficult as well. Have good water resistant sheet if you eat or drink in bed.