Blogger and Movable Type are pure server-side products. They run on a server only and all authoring is done through a web browser. Radio, by contrast, runs on your desktop or notebook computer and publishes to a server.
UserLand Software also offers UserLand Frontier (http://frontier.userland.com) that includes another tool called Manila (http://manila.userland.com). Manila provides equivalent functionality to a Blogger- or Movable Type-style blogging system.
A desktop blogging tool for a single blog.
An overall web content management system for any type of web publishing including large web sites.
Like Movable Type and Blogger, Manila runs on a server and all authoring is done through a web browser. Manila differs from Radio in that it is really targeted at applications beyond the level of individual blogs. Manila, for example, lets you build your own community of blogs. Though Frontier and Manila are technically separate, Manila is heavily used by virtually all Frontier customers.
Both Manila and Frontier run purely on a server (e.g., Windows NT, Mac OS, or Mac OS X) and all authoring is done through a web browser. Like Radio, Frontier includes a full object database, scripting language, script editor and debugger, outliner, multithreaded runtime, search engine, integrated HTTP server, full XML support, full RSS support, and distributed computing protocols, such as XML-RPC and SOAP.
Radio, Frontier, and Manila all interoperate. For example, you can use Radio as an authoring tool for your Manila site, taking advantage of Radio's enhanced editing features. While this is in no way required, it is a powerful combination.