I'm not a big lawn fan. I've been trying to eliminate as much of my lawn as possible. You can replace your lawn with a wild flower meadow if it's sunny enough. Check with your local county extension agent for a list of noxious and invasive plants in your area. You can also check the links page here for some information about invasive and noxious weeds.
Perennials are great for taking up lawn because they can require little care.
Plant some day lilies on a hard to mow slope. If you use many different varieties you can have blooms all summer long of different colors. Not bad for an easy to grow plant. It think the key to an organic lawn is really looking at which part of your lawn you use as a lawn. Concentrate on keeping your grass healthy there and convert the rest to easy to care ground covers and perennials.