I have a 1990 Brumby ute with an EA22 Engine conversion, this, thus, means there is no space for the spare wheel to fit in the engine bay any more.
Right now the spare's held in place over a wheel arch with a bike lock and a ocky-strap (messy, but functional).

The solution?
I have seen mounts on the roof, I have seen mounts on rear (guyph_01's wagon is a nice example), but for me the mount is going in the tray, on the passenger side.
I scouted my pile of junk from about the house and sheds and decided on some 13" rims of no use to me and a section of box-section to cut up for the rest of it.
For the project I went through 10 or so ultra-cheap Chinese welding rods that my grandpa bought years ago (He passed away ~10 years back, these are old rods and look corroded), 3 cutting disks and used half of a flapper disk for the angle-grinder.

Other than that the project has cost me $30 for some Wheel-hub bolts w/ nuts and some 10mm bolts w/ nuts from the local SCA.
How I went about it:
First up I cut up two 13" rims for their centers. I cut two up as I figured I might want a second holder one day or if I stuffed this first one up, or if someone I know wanted to make their own.
13" rim

The hacking begins

Double the freedom

Paint and rust removed on both via use of the flapper-disk

Cont.