I\'m aware of the excellent DevExpress LayoutManager & the half-attempts included in new releases of Delphi.
But I wonder whether an Open Source layout manager does
Project JEDI's JVCL free and open source component library includes a sort of a replacement, even that is maybe not as good as DevExpress one, but it has it's own good advantages. Is called "Jv Runtime design" and is installed within the standard JVLC setup (search for the components in the toolbar of the same name in the palette).
If you had never installed JVCL, note that you have to install JCL (Jedi Class Library before JVCL as this is a prerequisite) Look for the JVCL download zip file that includes the corresponding JCL package.