VOR DME perhaps?
Over at my airport (ESGG in Sweden) the MDA when GS is out is just 769ft (254 ft AGL) so you can get pretty close to ground without ILS

NDB approaches are common as well, they generally have higer minimas though.
However, most modern airliners can fly a fully automated approach by using GPS and the onboard Flight management system (RNAV). No navaids required at all...higher minimas than ILS of course but often lower than conventional NDB approaches.
On the boeing 737, when approaching the final approach fix, simply spin the alt. wheel to ZERO and fly the approach with VNAV/LNAV