As more and more texts from before 1800 are being put into electronic form by people without expertise -- whether scanned with OCR software, or typed by those without old-spelling knowledge (sometimes done overseas by those with little knowledge of modern English, let alone early modern) -- it becomes increasingly important to spot potential confusions of the long s and the letter f.
With the help of several people on the alt.usage.english newsgroup, especially David Vanecek and Mark Israel, I've assembled a list of words that will sneak past a spelling checker if the letters are confused. Searching a text for these words may give you a chance to spot potential confusions.
after and aster aster and after cafe and case cafes and cases case and cafe cases and cafes chafe and chase chafer and chaser chafing and chasing chase and chafe chaser and chafer chasing and chafing chefs and chess chess and chefs fable and sable fables and sables fag and sag fags and sags fail and sail failed and sailed failing and sailing fails and sails faint and saint fainted and sainted faintly and saintly faints and saints fake and sake fakes and sakes fallow and sallow falter and salter falters and salters fame and same fan and san fang and sang fat and sat fate and sate fated and sated fates and sates fault and sault favor and savor favored and savored favoring and savoring favors and savors fear and sear feared and seared fearing and searing fears and sears feat and seat feats and seats fee and see feed and seed feeder and seeder feeders and seeders feeding and seeding feedings and seedings feeds and seeds fees and sees fell and sell felling and selling fend and send fetter and setter fetters and setters fettle and settle fever and sever fevered and severed fevers and severs few and sew fewer and sewer fickle and sickle fight and sight fighting and sighting fights and sights fill and sill fills and sills filly and silly fine and sine fines and sines finger and singer fingers and singers fink and sink fins and sins fir and sir fire and sire fired and sired fires and sires fist and sift fisted and sifted fit and sit fits and sits fitter and sitter fitters and sitters fitting and sitting fittings and sittings fix and six fixes and sixes fizzle and sizzle flack and slack flam and slam flap and slap flaps and slaps flash and slash flashed and slashed flashes and slashes flashing and slashing flat and slat flats and slats fled and sled fleet and sleet flew and slew flick and slick flicker and slicker flicks and slicks flight and slight flights and slights fling and sling flings and slings flip and slip flipped and slipped flips and slips flit and slit flop and slop flopping and slopping floppy and sloppy flops and slops flow and slow flowed and slowed flower and slower flowing and slowing flows and slows flung and slung flurry and slurry fly and sly fob and sob fobbing and sobbing foggy and soggy foil and soil foiled and soiled foiling and soiling foils and soils fold and sold folder and solder folly and solly foot and soot fore and sore forest and sorest fort and sort forts and sorts foster and softer fought and sought foul and soul fouls and souls found and sound founded and sounded founder and sounder founding and sounding founds and sounds four and sour fours and sours fuck and suck fun and sun funder and sunder funk and sunk funny and sunny future and suture futures and sutures gift and gist gist and gift heifer and heiser Heiser and Heifer infect and insect infects and insects insect and infect insects and infects leafed and leased leafing and leasing leased and leafed leasing and leafing left and lest lest and left life and lise lift and list lifted and listed lifter and lister lifters and listers lifting and listing lifts and lists Lise and Life list and lift listed and lifted Lister and Lifter listers and lifters listing and lifting lists and lifts loft and lost lost and loft rafter and raster raster and rafter ruffian and russian ruffians and russians Russian and Ruffian Russians and Ruffians saber and faber sable and fable sables and fables sag and fag sags and fags sail and fail sailed and failed sailing and failing sails and fails saint and faint sainted and fainted saintly and faintly saints and faints sake and fake sakes and fakes sallow and fallow salter and falter salters and falters same and fame sang and fang sat and fat sate and fate sated and fated sates and fates savor and favor savored and favored savoring and favoring savors and favors sear and fear seared and feared searing and fearing seat and feat seats and feats see and fee seed and feed seeder and feeder seeders and feeders seeding and feeding seedings and feedings seeds and feeds sees and fees sell and fell selling and felling send and fend setter and fetter setters and fetters settle and fettle sever and fever severed and fevered severs and fevers sew and few sewer and fewer sickle and fickle sift and fist sifted and fisted sifter and sister sight and fight sighting and fighting sights and fights sill and fill sills and fills silly and filly sine and fine sines and fines singer and finger singers and fingers sink and fink sins and fins sir and fir sire and fire sired and fired sires and fires sister and sifter sit and fit sits and fits sitter and fitter sitters and fitters sitting and fitting sittings and fittings six and fix sixes and fixes sizzle and fizzle slack and flack slam and flam slanders and flanders slap and flap slaps and flaps slash and flash slashed and flashed slashes and flashes slashing and flashing slat and flat slats and flats sled and fled sleet and fleet slew and flew slick and flick slicker and flicker slicks and flicks slight and flight slights and flights sling and fling slings and flings slip and flip slipped and flipped slips and flips slit and flit slop and flop slopping and flopping sloppy and floppy slops and flops slow and flow slowed and flowed slower and flower slowing and flowing slows and flows slung and flung slurry and flurry sly and fly sob and fob sobbing and fobbing softer and foster soggy and foggy soil and foil soiled and foiled soiling and foiling soils and foils sold and fold solder and folder soot and foot sore and fore sorest and forest sort and fort sorts and forts sought and fought soul and foul souls and fouls sound and found sounded and founded sounder and founder sounding and founding sounds and founds sour and four sours and fours suck and fuck sun and fun sunder and funder sunk and funk sunny and funny suture and future sutures and futures wife and wise wifely and wisely wise and wife wisely and wifely