Obey Your Uniform
 

Here's a long term dare I always enjoyed. Its pretty flexible, but I'll give some examples.

Set rules for what different types of clothing, and obey them whenever you wear them.

a few examples:

Whenever you're wearing a hat, no speaking.
Whenever you're not wearing a jacket, you must tell the truth at all times
If you're wearing socks, you must speak quietly and gently at all times
If your knees are showing (skirt, shorts, etc) you must agree to any task or favor anyone asks of you.

You can go where ever you want with these, and be as specific or as general as you want. Its the structure that is important, especially once your clothing options move out of your control (weather, or setting/circumstances, laundry, etc).

Great Dare!

Very flexible, but simple and easy to understand.

This is a preety good and simple dare.You could also make diffrent rules ex.If your wearing a tank-top you must only speak when spoken to etc.

Another fun twist: add some chain-reaction rules, like if you're wearing a sweater, you can't wear a jacket, or if you're wearing sandals you have to wear shorts. Or you have to wear a hat on Saturdays. Get yourself into some real trouble.

you shoud structure it so instead of just giving the idea maybe post back with a whole structure for people to follow, would be intresting to see how the same constraints effect different people.