An article from wildaboutgardens.org explains how to setup your lawn to be more wildlife friendly. It might take a while to get the results, depending on what you're starting with, but there is a diverse array of tips and suggestions.

Personally I'm quite keen to keep an area of lawn largely unmown as a wildflower meadow, but it remains to be seen just how easy that will be. I might end up with a scrappy and unkempt bit of lawn that falls rather short of the romantic vision of tall grasses and poppies swaying in the breeze.