The answer to this question strongly depends on what do you want to humidify.
If you have only a few cakes, then perlite is probably the humidification of choice.
With casings, the moisture that escapes the casing might already be enough to humidify for a mono tub.
If you have a shelf like grow system, a cool mist humidifier or DIY humidification bucket with ultrasonics might suit your needs.
If you have a large room you might want a few ultrasonic misters in a tote and/or a swamp cooler.
If you have a commercial sized grow a hydrofogger system or residential swamp cooler should fit the bill.
To decide on what you want to use, please refer to the Humidification Techniques