Olympic Hands on the Land - Cycles
From the National Park Service, animated diagrams of the water, nitrogen, and carbon cycles. Includes explanations.

Life Materials and Nutrient Cycles
How life shares materials, why we need each other's "leftovers," water cycle, carbon cycle, nitrogen cycle, and sulfur cycle, including diagrams.

Water What Ifs - Water Quality and Nitrates and Phosphates
Shows the inter-relationship of these surface water parameters.

Biogeochemical Cycles
A brief look at the major nutrient cycles, including pictures.