I have need for more individual items to create different linear slide mechanisms.

This thing is a bushing block. It can take a bushing, flanged or otherwise, and use that as its internal slide mechanism. The topside is adequate for tapping to whatever size you need. The length is about an 1.5", but you can make it any length and width you want by editing the OpenScad file.

It works fairly well, particularly if the bushing is the same length as the pillow block.

Depending on the tolerances of your printer configuration, you may need to print the radius larger or smaller. In my own uses, I don't utilize a set screw. I just make the hole fairly snug, and then heat it up to press fit the bushing in.

I have found that once it's in there, it really isn't coming out easily. If that's not enough, a dab of epoxy or other strong binder would probably seal it more permanently.

UPDATE: 27012011
changed the design based on feedback from Marcus to include mounting holes, and some smoothing on the connection between the bushing and the platform piece.

The mounting holes are M3 by default, but can easily be changed in the OpenScad file, or even eliminated by setting to zero radius.

I have not actually printed and photoed this design yet, so the photos are the original design.

1) Excitedly look for places where you could possibly utilize a bushing pillow block.
2) Print one or more of these out to suit your needs
3) Insert a bushing into the hole
4) Slide your bushing block onto a smooth steel rod
5) Rejoice!