Pour about a tablespoonful of ordinary vinegar into a saucer and leave it on a worktop. It is, of course, best to do this when you start the cooking process rather than after it has happened.
I like to put a little pan of water with some cheap cinnamon sprinkled in it on the stove to heat while I cook - it smells stronger than fish OR brussel sprouts.
A 'Glade' / Ambi pur candle always neutralises cooking smells, jmck...always buy the strong smelling ones, (have a sniff in the shop) citrus or cherry are two that I have used - light before you start cooking...
If cooking fish in a microwave...slices of lemon in a bowl of water afterwards (10 minutes on simmer mode) will eliminate the odour...
As a follow on from Quizmonster, I find the vinegar smells if just left out. Put into small bowl, cover with cling film and peirce lid serveral times. But yes, ditto, works better before cooking!