From the perspective of a canyoneer here are my thoughts.
Emphasis for me is that you need a retrievable rope system and don't want to simply abseil from a double rope for whatever reason, this may be down to not having a long enough rope or using a descender specific for single ropes which you find a lot with rope access and caving descenders.
If you have adequate rope for a double rope but would prefer to ab from a single strand only then a common method is to use a biner block.
Essentially clove hitch your rope to a carabiner (preferably steel) at the required length and then feed the end of the rope through your anchor point (if it is suitable i.e not likely to cut the rope). Then ab from the single cord and pull the other end to retrieve the rope. Be sure to ab from the correct end and be sure to trust your bolt or anchor.
Certainly in canyoning and when descending from pinnacles etc. it is not unheard of to use 'sacrificial' kit for anchoring. Usually a length of cord or sling coupled with a maillon or rap-ring as shown below. Expect to pay about 2 quid for a new alloy rap ring.
Alternatively when a tree or similar bollard is used as an anchor then a figure of eight and a biner can be used in a similar manner...
http://static-dev-climbing.s3.amazonaws.com/wp-content/uploads/2012/11/Long-Rappel-Short-Rope.jpg
Screw up B ab from C and pull on A to get the rope down.
If A is not long enough then for me, best practice is to use a pull cord. Just a long thin rope or cord for rope retrieval. For example a 200 foot rope with a 200 foot pull cord is lot lighter than having to carry 400 feet of rope. Coupled with a safe technique for rope retrieval and your on to a winner. Just don't use the pull cord for load bearing (asides sack hauling etc).
Lastly, now all sensible ideas have been exhausted there is the sheep shank...
I have tried this in the climbing wall and it works but is lunacy - there will nearly always be an alternative.
Tie the rope to the anchor, then below that tie the sheep shank, load your weight on to the rope and before departure cut the middle strand as in the picture.
SNIP!!!
Don't cut the wrong one and don't unload the rope early and you may live! Unload the rope and you will retrieve all but a metre or so which will remain hanging from your anchor as a warning to others lol!
Have a look here it's quite good:
http://bigfootmountainguides.com/2012/01/31/how-to-use-a-pull-cord-for-rappelling/
And lastly please go and practice in a climbing wall where someone can belay you.