I try and do : soup indeed in single size containers in the freezer, savoury quiches/tart/cakes, single size of veggies or casserole to re-heat. I usually pair something like (cake or tart slice or rice or pasta based casserole type dish) + (soup or salad or veggies).
I also freeze or refrigerate crepes/small breads/pita so I can replace the quiche with a small sandwich.
I find the tarts/cakes/sandwich idea quite practical, because they are easily transportable and do not need cutlery, and with the salad or soup, it makes it quite a balanced meal. Also you can put anything you like in them to keep things varied and interesting.
Today I am having for example crepe filled with cream cheese and ham, and a small salad of radicchio, pecorino, apple and onion. I keep a small bottle of oil and vinegar by my desk, so everything is right there. I take single extra servings of salt/pepper/sugar/sauce from the coffee shop when I buy coffee and also use them as needed to add into soup or salad or yogurt etc.
Ah yes, for the salad, I cut the ingredients directly at work to keep them fresher, so I can use them over several servings (we have a fridge) but I am guessing it is also all right to pre-cut at home without the seasoning.