Wow, I had no idea this was a thing! I live on a boat in the UK and fight a constant battle to reduce condensation and humidity. Things I've found which make my job harder, and so may help for you, include:
As mentioned boiling a pan will help, but doing it just to humidify is a waste. Instead you can multitask by:
- Boiling pasta
- boiling a tea kettle - when you're British that happens a lot. Benefit is that you can drink the tea!
- keeping a stock pot, pot of stew or soup simmering on the stove.
Also I've found:
- hanging washing as mentioned, bonus points if it's over a radiator
- breathing - humans generate moisture while breathing. You can increase the output by increasing the number of humans (have a party, get room mates) or the rate of breathing and exertion of the inhabitants ;)
- get a dog or cat, these will also breathe for you. Added benefits from tracking moisture in on their fur!
- ironing, especially with an electric steam iron so heavy cottons are best. If you don't have enough ironing of your own you could start a side hustle taking in other peoples' thereby generating an extra income at the same time
Hope some of this helps