Just added a load of new layouts to http://www.thortrains.net In the HO and N section are layout plans for both scales, many of which are designed for small spaces. They can be used as is, or as expansions to existing layouts.
In the O/O27 section we have added many layouts. Some were added to the “Classic O and O27” heading, others to “O and O27 on a budget”.
Enjoy them!