We've recently seen a few interesting Internet services focused on doing one thing -- one very small thing -- and striving to do it very, very well. These include the Twitter blogging service, Jott for recording 15-second voice messages and transcribing them using speech recognition, and Remember The Milk and Imified for to-do list management.

Twitter is a blogging service that does less. Blogging has become a pretty complicated affair nowadays, with fancy layout controls and RSS feeds and multimedia integration. Twitter is simple: You can post anything you like, so long as it's a text message, and fits in 140 characters or less. No formatting, no layout, no multimedia, no RSS. You can post using a Web interface, by IM or text message, or by feeding messages into Twitter using an RSS feed. Similarly, you can read Twitter messages on the Web, by getting instant messages, cell phone text messages, or RSS feeds. And that's pretty much all there is to Twitter.

Twitter is sweeping the Internet, exploding in popularity. For an in-depth look at Twitter, see our recent article, which includes interviews with Twitter co-founder Evan Williams and several Twitter aficionados. And TechCrunch compares Twitter with a couple of similar services: Dodgeball and the Facebook status service

I tried Twitter myself for a couple of days last week. My wife pointed out later that most of my posts related to food -- I was thinking about eating, planning to eat, wishing I was eating, arranging to eat. I'm a man with powerful appetites.

Jott is a service designed to allow you to make notes to yourself even when your hands aren't free to write things down, such as when you're driving, walking through the airport, or fleeing in panic because you're on fire. You call Jott's toll-free number from your cell phone and leave a message up to 15 seconds. Jott transcribes the messages using speech recognition and e-mails the result back to you. For more on Jott, see our first-look review.

My colleague Barbara Krasnoff recommends two services. One, with the cute name Remember The Milk, allows you to create simple to-do lists and read them from e-mail, SMS, instant messenger, RSS, and more. Barbara likes the way it integrates with Google Calendar.

She also says Imified is worth looking at. It's a service that allows you to send reminders to yourself via instant message.

Know about any good, ultrasimple Internet services? What's your favorite?