From my Will it Freeze book -" use small courgettes, about 3 inches long, slice thinly, either blanch in boiling water for one minute, or saute in butter for one minute. Cool and freeze on trays, then pack into containers. Keep for a year - to reuse, if blanched, cook from frozen in water, if sauteed, sautee them from frozen".

we used to call it blanch and refresh-- one minute in boiling water & one minute in iced water-- then dry off and freeze as Bamboo says
freeze some tomatoes & onions and you've almost got ratatouille!!

alternatively chuck tomatoes, courgette & onions into a pan, boil till cooked, cool,bag,freeze. Great sauce starter for spag bol etc & uses up some of the surplus garden produce.