I just look for web hosting control panel software or some software to control web server, database server, etc...
Most software is base on Linux; InsPanel is software for Windows. I think VHCS is best software for open source Linux web hosting control panel, also Webmin quite interested for dedicate server as well.
VHCS delivers a complete hosting automation appliance by offering significant security, total-cost-of-ownership, and performance advantages over competing commercial solutions.
With VHCS Pro you can configure your server and applications, create user with domains with a few point-and-click operations that take less than a minute. There is no limit to the number of resellers, users and domains that can be created.At the core of VHCS Pro are 3 easy-to-use, Web-based control panels. VHCS provides graphic user interfaces for the administrators, resellers and users.
How to install? I recommend the article HostingHacks.net - Build an Apache Based Web Hosting Service.
ISPConfig is an open source hosting control panel for Linux. ISPConfig is licensed under BSD license.
SysCP, the System Control Panel is a server administration tool which enables an internet service provider to give their customers a web-based application to administrate their email addresses, their sub domains etc.
Domain Technologie Control
Domain Technologie Control (DTC) is a GPL control panel for hosting. Using a web GUI for admin and accounting all hosting services, DTC can delegate the task of creating subdomains, email, and FTP accounts to users for the domain names they own. DTC manages a MySQL database containing all the hosting information. It has support for many programs (bind 8 and 9 and compatibles, MySQL, Apache 1.3, php4, qmail, postfix 2, courier, dovecot, proftpd, webalizer, mod-log-sql, etc.) through config files and/or MySQL plugins (when the service is non-critical). It can also generate backup scripts, calculation scripts, and config files using a single system UID/GID and monitor all traffic accounting per user and per service. Since version 0.12, DTC is fully skinable and translated in 10 languages (Chinese, English, Spanish, French, Dutch, German, Italian, Russian, Hungarian and Polish).
In shorter words, DTC is THE open source hosting software you need for your everyday server administration if you do web, dns, ftp or mail hosting.
InsPanel (Windows only)
This is commercial software, but free for 10 website. InsPanel is a web-based remote control application designed with the shared hosting provider in mind. It is ideal for hosting providers looking for a low-cost scalable solution for clients
web-cp is a full-featured, open source web hosting control panel written in PHP and released under the GPL. It consists of 4 control panels: personal, domain, reseller, and server. web-cp runs on almost every version of Unix/Linux/BSD and only Apache, MySQL and PHP are required.
Webmin is a web-based interface for system administration for UNIX. Using any browser that supports tables and forms (and Java for the File Manager module), you can setup user accounts, Apache, DNS, file sharing and so on.
I think Webmin is not fit for web hosting business, but it very cool for conrol server via web browser.
Xpanel is the ultimate community building program. Allowing you to give your visitors a free web site on your server. With complete control over every aspect of your free web site program, you can grow page views, revenue and brand awareness for your site. XPanel run on Linux and is written completely in Perl and uses MySQL as a database back end.