Markdown service bliss
It exists. Oh, and if you're using any of Brett Terpstra's awesome tools, be sure to put some money in the tip jar on the right side of his page.
I produce more with Brett's fork of Notational Velocity than most paid software I own. If you feel the same way, the least you can do is give the guy a little money for coffee. . . or beer. . . or whatever liquid refreshment fuels his productivity.