I use Posterous for blogging, and do all of my posting through Mail.app
I do a lot of kottke-sullivan-style posts in this format:
The New York Times reports:
Blah blah blah
But what should be a pretty easy process takes a lot of work, and it's too much work to get done on an iPad comfortably.
I'd like to have a bookmarklet where I could just select the paragraph (Blah Blah Blah above) to become the block quote and have it instantly create a new message in Mail.app or iOS Mail with the url in a link ready to turn into "The New York Times reports:" or "John Gruber riffs:", then the block quote, then I can just type in my comments and send it off.