Tsukemono are a huge part of the average Japanese meal. They're one of the reasons you'll see a very pretty set meal that screams variety. All sorts are available for purchase in lots of grocery stores, and there are so many different recipes that it's most likely impossible to catalog them all.
Highly popular at all times, tsukemono are both a wonder and a potential health risk. Such things as the "seaweed salad" available at most sushi stands in the U.S. are relatively healthy and nutritive dense, but often loaded with calories as well. Then there's the fact that Japanese pickles use lots of vinegar, salt, and (sometimes) some carcinogenic elements. If you're eating takuan or fukujinzuke three or more times a day, you might have some health problems when you're older - Japan has the highest rate of digestive tract cancers in the world!
Often, tsukemono is taken to mean pickle. In the traditional European sense that's not always the most correct word. Many are simple flavor combinations or treatments (like seaweed salads or nukadoko) meant to be consumed right away while others (like takuan or umeboshi) are truly preserved vegetables. Seeing as nukadoko ingredients can be hard to come by at times, I haven't taken that leap yet, though I plan to in the future.
Often used to stretch a meal, and just as often used as a "chopstick rest" much like sorbet or a cheese course between courses in a finer European style, there are plenty of reasons to keep a few simple ones around that can be used as okazu. I have a few standard ones that I keep in supply here in the house, and sometimes they're all one needs to have with a bowl of rice and some miso.
My favorite one is a simple fridge pickle of small kyuuri (small seedless cucumbers similar to those you'd make dill pickles with) and wakame in a vinegar dressing.
Recipe: Kyuuri to wakame aemono
Serves: 4 +
3-6 seedless cucumbers
3-6 tablespoons fueru wakame
1 tablespoon kosher salt
4 tablespoons rice vinegar
1 tablespoon sugar
Slice the cucumbers as thinly as possible - I usually use a Benriner branded mandolin on a 1mm setting. Place in a bowl and sprinkle them with the salt, then rub the salt in and let them sit for a few moments to draw some of their moisture off.
Reconstitute the wakame and discard the water. Squeeze the excess water from the seaweed, and place in the bowl with the cucumbers. Add in the remaining ingredients, and stir to combine them. They're ready to consume in about an hour, but are best the next day.
Adjust the vinegar content as you like, depended on how pungent or sour you want your pickles to be. This usually lasts about a week in the fridge.