This new iPhone app from Greg Pierce at Agile Tortoise reminds me of Birdhouse, but on steroids. It launches straight away into an empty text box so you can jot down any thought or note you like. From there you can save the draft of the note you just created or share it via Twitter, email, etc. It even supports Markdown export.
I like how Federico Viticci calls it a “Launch Center for text”. And Dave Caolo and Stephen Hackett both too have written brief reviews.