The paper by that title by T.K. Pratt (in Focus on Canada, Sandra Clarke [no relation], ed., 1993) combs various sources on U.S., U.K., and Canadian spelling. Pratt concludes that there is little agreement, a statement that is harder to make 13 years later.
Nonetheless, here are all the words Pratt lists whose spelling varies among the countries (not always with one spelling per country). I’m using the first-listed Canadian Oxford spelling in all cases, as life is too short to jot down every variation. (Pratt’s article is an excellent example of how not to typeset anything, including tables, which border on unreadable. This took a lot of futzing.)
- colour, favour, glamour, honour, humour, labour, odour, stupor
- coloration, colourful, favourite, glamorous, honourable, humorous, laborious, labouring
- centre, lustre, macabre, meagre, metre, spectre, theatre, timbre
- defence, licence (n.), license (v.), practice (n.), practise (v.)
- annul, compel, distill, enrol, enrolment, expel, fulfill, install, instalment, signalled, skilful
- benefited, equalled, focused, imperilled, kidnapped, outfitted, signalled
- jewellery (a bugbear of mine: I write jewelry and think “jewellery” is made of “jewellers”), libellous, tranquilize, woollen, worshipper
- advertise, civilize, criticize, realize, surprise
- analyze, paralyze
- acknowledgement, aging, judgment, livable, lovable, movable
- æsthetics, anæsthesia, encyclopedia, medieval
- fetus, manœuvre (but Cf. fibre optic, fibreglass)
- appendices, bureau, chateaux, formulæ, indexes or indices (latter given first for “technical use”), referendums, tableaux
- æroplane, analog (!), axe, catalogue, cheque, cigarette, connection, curb, dialogue, disc, draft or draught (depending on sense), grey, gypsy, inflection, mould (mold listed as variant), omelette, plow, program, pyjamas, snowplow, storey (building), toward (not towards)