Experience Chart

Credit for this excellent chart goes to Somnus of Criddia, because i sure as hell didn't do all that math. The chart has the effect of making progression up until level 9 fairly smooth and easy, and then progressively more difficult as you climb in levels. Perfect for a setting like Eberron, where low and mid-level characters are ubiquitous, but the more awesomely powerful ones are significantly rarer than in most settings.