I too cannot use a whole "bunch" of celery before it goes bad. One of our
nearby stores sells it by the stalk - great if you need just a bit fresh.
But what I usually do is to buy the whole bunch - when I need some, or
when it's on sale - use what I want that day, and chop up the rest and put
it into ziplock bags in the freezer (no blanching). It works fine to
throw into soups, stews, even stirfry later. You can do the same thing
with peppers or onions....although the frozen onions should be cooked on
own a bit before adding other ingredients. You can also freeze tomatoes
this way - to be used later in cooking. Just pop the whole tomatoes into
a bag and freeze. To use, run under hot water briefly to release the
skin, and then toss the tomato into your pot of stuff.