Herbs

In part it depends on the Herb... after all some are deciduious (drop thier leaves naturally in the winter and come back in the spring) and others such as parsley are really only anuals anyway. But a tight bushy lavender, sage or rosmary will deal quite happily with a blanket of snow and/or tempratures down to -10 (and proabably a bit more), as well as frozen soil for a week or so, as mine have done just fine with this kind of weather. As for Mint and Lemon balm they seem to be almost indistructable... with prehaps the exception of severe drought... when they just drop leaves and wait for better conditions.

I supose it depends on how long and how cold your weather gets matced with how much window-space you have and what plants you want to grow.

As a rule of thumb if it is a woody herb then (as long as it is a tight bush and at least a year old) it will do fine outside in the above mentioned conditions. Lighter herbs, ones with fleshy leaves or root corms (like chives) will tend to sleep the winter and return in the spring. And fully fleshy herbs are either anuals or die at the first frost... they also tend to be a lot less drought resistant too.

Can I also make a note about collecting from the wild (as was mentioned by one poster).
This is fine in practice, but you REALLY need to know your plants as there are many relitives that either have no effects or adverse ones, be very cercomspect with your collecting and be aware of the laws on ownership, protected lands and plants... esspecally in the UK many places are privatly owned, or the plants are rare enough to be either protected by law or caution should be practiced so as not to wipe the population out.
With that in mind (and with permissions of landowners) foraging is a fantastic way of getting not just free magical herbs, but food and a whole new insight into nature.

Be bright, be bold
Fillionous