webapp creation...

hi... I'm looking to create a webapp. I'd rather not spend my wheels spinning on creating functionality from scratch when it already exists in other apps. so, I'm trying to find out if there are good 'starting' templates/shells that I might be able to use as a starting point. I've seen various plain web templates that cover the look/feel. I've also seen the open source CMS kinds of solutions (Mambo/phpBB/etc..) that I could use to rip apart for an initial starting point for the functionality that I'll need.. I've also taken a look at the Pear/Smarty solutions, but they're not quite what I'm searching for... I'm looking for a starting app that would have menus/submenus, user registration/login/management/admin section as a start... I could then incorporate the functionality that I'm looking to create... Basically, I'll add a number of sections to manage software that I'll be creating. The end site won't be a CMS app, but I could rip out of an app what I need. The issue I've seen with some CMS apps is that they appear to write 'everything' into a db!!! (which kind of makes sense if you're creating an app for use by lots of users/operators) I'm more concerned with the functionality of the app than the look/feel. There is also somewhat of a time constraint. So, Thoughts/Comments/Etc... are all helpful. Thanks!