Ubuntu Server Team recommend this 2 option:
1.- OpenSSH Server
2.- eBox is a web framework used to manage server application configuration. The modular design of eBox allows you to pick and choose which services you want to configure using eBox.
see details here
3.- in ubuntu server 10.10 ebox was changed with Puppet is a cross platform framework enabling system administrators to perform common tasks using code. The code can do a variety of tasks from installing new software, to checking file permissions, or updating user accounts. Puppet is great not only during the initial installation of a system, but also throughout the system's entire life cycle. In most circumstances puppet will be used in a client/server configuration. more details here
4.- in ubuntu server 12.04 the team introduce Zentyal is a Linux small business server, that can be configured as a Gateway, Infrastructure Manager, Unified Threat Manager, Office Server, Unified Communication Server or a combination of them. Zentyal consists of a serie of packages (usually one for each module) that provide a web interface to configure the different servers or services. The configuration is stored on a key-value Redis database but users, groups and domains related configuration is on OpenLDAP. more details here