One of the best plugin to create is MyThemeShop launcher.
And it is free.
I am a member of a paid subscription in MyThemeShop, and their plugins work great. I use the plugin WP Review and also WP Quiz. There are bugs, but they fix it soon after the bug report. OK, enough about Mythemeshop.
Launcher plugin is good to make under construction or coming soon page. It has integration with many email marketing tools such as MailChimp, Aweber. You know, usually the “coming soon” page has an email form to let the visitor know when it will be launched. (You may read about email marketing at 7 Most FAQ of Email Marketing You Must Know)
It also has counter to let visitor know when your web will be launched.