Depends on what you're wanting to grow.

You need both good light and high humidity for: Calathea, Codiaeum, Araucaria, Dieffenbachia, Anthurium, Stelitzia, Hedera, Cordyline, Coffea, Radermachia

These don't need high humidity, so long as the light is decent: Dracaena, Chlorophytum, Yucca, Ficus, Hoya, Haworthia, Aloe, Setcreasea, Tradescantia, Crassula, Kalanchoe, Euphorbia, Plectranthus, Agave, Gynura, Pedilanthus, Beaucarnea, Dieffenbachia (for some people), Rhoeo, most/all varieties of cactus

These don't need strong light but do want humidity: Fittonia, Davallia, Asplenium, Maranta, Cissus?, some Philodendron

These can get by without a lot of light or a lot of humidity, though almost all *prefer* some of both and won't necessarily look their best under dim dry conditions: Syngonium, Aglaonema, some Philodendron, Zamioculcas, Spathiphyllum, Sansevieria, Epipremnum, Monstera, Aspidistra

Disclaimers and Caveats:

This is not an exhaustive list: almost all of these are families of plants that I've grown at one time or another, and either what worked in that situation or what *would* have worked if I'd been able to provide it.

In many cases, the light and humidity requirements depend on other factors too: the time of year, the temperature, etc.

"Strong" or "decent" light may or may not mean direct sun: there are several families of plant that like sun that's as bright as possible without actually being direct sun, and will burn and die in direct sun.

Good air circulation is pretty important with humidity-loving plants; otherwise there can be rot issues.

The same plant may behave differently for different growers, or in different houses. It's weird, but it happens.

There are also some plants that I've never been able to figure out: Peperomias and I, for example, just don't get along despite numerous attempts, and we have reluctantly had to just agree to break up and see other plants/growers. I'm relatively new and unconfident with bromeliads. Haven't been able to make any palms work so far, and don't try often, either. No experience with Citrus at all. I just don't *like* most flowering plants (Cyclamen, Begonia, Clivia, Saintpaulia) that much. I'm not convinced that *anybody* can grow Stromanthe or Ctenanthe. Etc. Which maybe someone will fill those in.

But the basic answer to your question is: it depends on what you want to grow.

Mr. Subjunctive,
You really think you don't need high humidity for dracaena, hoya, and beaucarnea?? I don't know...I really disagree. But everyone has their own opinion. Ever since I've used humidity trays for my hoyas, my dracaena marginata and my beaucarnea recurvata, they've been thriving. I've also read that they like humidity, and lots of it. Just posting a new opinion :-)
Gabi

I definitely believe in humidity during the winter. I've called a plumber to come tomorrow because the humidifier on our furnace isn't working. Never mind the houseplants; my nose and head are suffering.

I also got a cool mist humidifier for the plants. I wanted a warm-mist but couldn't find one. I read somewhere that they are less popular because the big thing lately is people are afraid of mold. For Petes sake! I always used warm mist before and never worried about mold.

The plants do seem to like the extra humidity because the sunroom I have them in has a gas fireplace which virtually SUCKS moisture from the air.

Gabro14 --

Well, I'm not saying that they mind extra humidity. But I've been able to grow them fine without going out of my way to give them extra. [shrugs] My plants are also numerous and (mostly) in fairly close groupings, which may account for some of the difference.

Let's remember, too, that everyone's home is different. We keep our inside temperature set lower in the winter and higher in the summer than most people. This, of course, results in humidities that are naturally higher.

I've never done anything to increase the humidity for my plants in anyway, and I assure you that they are thriving. But if the humidity levels were very low, I'm sure that I'd see different results.