ActionMenu (mentioned in Josh’s JB Favourites post) is currently one of those jailbreak tweaks I can do without, but I may well jump aboard the ActionMenu bandwagon if Ryan Petrich gets around to releasing the features he teases in the screenshot above. Rich text capabilities within Mail.app? Yes, please!
[Party Pooping Time: Err, before anybody gets too excited about all of this, I'm guessing that all that @rpetrich has done here is to add the relevant HTML tags to those Bold and Italics buttons. I doubt this is an actual hack to get rich text editing working everywhere on iOS.]