How is mutualism similar to and different from commensalism?

Both mutualism and commensalism involve a close relationship between two organisms where at least one of them benefits.

In mutualism, both organisms benefit while in commensalism one benefits and the other is unaffected.

These examples are from other sources found on-line.

The bee and the flower. Bees fly from flower to flower gathering nectar, which they make into food, benefiting the bees. When they land in a flower, the bees get some pollen on their hairy bodies, and when they land in the next flower, some of the pollen from the first one rubs off, pollinating* the plant. This benefits the plants. In this mutualistic relationship, the bees get to eat, and the flowering plants get to reproduce.
(source – http://www.necsi.edu/projects/evolution/co-evolution/mutualistic/co-evolution_mutualistic.html)

An example of commensalism: cattle egrets foraging in fields among cattle or other livestock. As cattle, horses and other livestock graze on the field, they cause movements that stir up various insects. As the insects are stirred up, the cattle egrets following the livestock catch and feed upon them. The egrets benefit from this relationship because the livestock have helped them find their meals, while the livestock are typically unaffected by it.
(source – http://ngm.nationalgeographic.com/ngm/photo-contest/2011/entries/113986/view/)