Yes.
However, at this time it probably requires you to get your hands a little dirty. For shrinking DVDs, one user recently
posted a thread showing step-by-step how to shrink a video down to fit on a smaller DVD. He's also working on a shell script to automate some of it, which may make it easier for the general user. Just to clear up any misconceptions - shrinking a dual-layer commercial DVD down to fit on a single-layer recordable DVD
will reduce quality (unless you're just picking and choosing the portions of the larger DVD that you want to keep).
But as for finding a full-featured program similar to DVD-Shrink for Windows, as far as I know that has not arrived for Linux yet. Soon, I hope
I've written a few little utilities for things like video conversion, making DVD menus and stuff. Get it
on sourceforge.