Firing up NetNewsWire (Yes, I gave up on NewsFire), I sniffed a nice scented wind from incorporated subversion of a new plugin that allows users to subscribe to a WordPress blog and get blog postings via email. Called Subscribe2, this is one plugin that many bloggers I know would love so they can really stick it to their readers.
Having used Movabletype before WordPress, I believe Movabletype has had this feature for a while, even before the days RSS became mainstream / popular. Other solutions for WordPress exist, such as RSS2email, but they are way more complex to install and run (think cron jobs).
Subscribe2 does what you’d mostly expect from a “subscribe via email” plugin, including allowing you to mass subscribe your buddies to your blog by email (SPAM!), managing subscribers at will, editing all outgoing messages and a lot more. Like James Farmer of InSub said, I would also love a daily digest email rather than an email per post, but it is rather cool that readers get the “breaking news” straight from the source, especially for irregular bloggers like myself.