"Ultralighting" is the listening equivalent of Amateur Radio's QRP. That is, trying to get the best results from the most simple equipment, a kind of back to basics if you like.
FM DX can be as complicated as the enthusiast makes it. Many use expensive tuners, sometimes modifying them. They use outdoor antennas sometimes designed specifically for DX reception rather than domestic listening. Other additions can be receivers to monitor below the FM band so as to know when an opening is about to occur. Very quickly one can run into high costs and a room full of gear!
So, when the Ultralight AM listening "craze" took off in 2007 thanks to American radio enthusiast Gary De Bock it was only a matter of time before the scaling back of our pursuit would be extended to the FM band.
Small receivers employing digital signal processing have come on the market in the last couple of years making it possible for excellent results to be achieved cheaply. These receivers, designed for domestic listening have superb sensitivity and selectivity and some even have inputs for external antennas.
Information on radios commonly used by Ultralight fans can be found here: http://www.dxer.ca/file-area/cat_view/87-ultra-light-radio-files-area/94-ultralight-radios
General Ultralight information: http://www.dxer.ca/file-area/cat_view/87-ultra-light-radio-files-area
My own preference is for the Chinese made Tecsun PL310 receiver, review here: http://www.dxer.ca/file-area/doc_download/270-the-tecsun-pl-310-am-lw-fm-sw-dsp-receiver
Ultralight Yahoo group: http://groups.yahoo.com/group/ultralightdx/
563 stations in 33 DXCC countries