Should I use an FTP server as a maven host?

You might want to have a look at Nexus, a Maven repository manager. We've replaced our local Maven repository with a Nexus-based one and find it tremendously useful.

I've successfully used Archiva as my repository for several years ... see http://archiva.apache.org/. It's easy to administer and allows you to configure as many repositories as you need (SNAPSHOT, internal, external, etc).

According to the book "Better Builds with Maven", the most common type of repository is HTTP, this paragraph describes what I think you need:

This chapter will assume the repositories are running from http://localhost:8081/ and that artifacts are deployed to the repositories using the file system. However, it is possible to use a repository on another server with any combination of supported protocols including http, ftp, scp, sftp and more. For more information, refer to Chapter 3.

A Maven 2 repository is simply a specific directory structure, so once you get the transport and server specifications right for the repository and deployment portion of your POMs, it should be completely transparent to your users.

You can even use Dropbox. All that you need is a public address to access the files generated with mvn deploy, with any of the protocols in the accepted answer.

I guess there are more services that can work in the same way, but I'm not certain about the URL schemes that alternatives to Dropbox may use.