It's that time of year again, when the first frost renders my herb garden unusable. It's a sad day in the Princess household, I can tell you. I just can't cook without my lemon thyme anymore. Luckily though, I don't have to.
Last year I stumbled upon the perfect method for preserving cut herbs for use in cooking. I go out the day before the frost is expected and harvest as much as I can. Or in the case of the mint and oregano, as much as I think I can use. (I believe in five years my herb patch will have evolved into a pitched battle between the mint and the oregano for dominance.)
For each herb I have ready one wet paper towel, not dripping wet, but more than damp, and a plastic storage bag. I like quart size freezer bags, but gallon would be nice if you've got that much to harvest. Place the paper towel in the bottom of the bag and then just stuff the herb in after it. You probably don't want to be too rough, but remember herbs are basically weeds we've found a use for, so don't worry about being too nice either.
Store each bag in your fridge. I keep mine on the bottom shelf, mostly because things near the top tend to freeze for some reason. (I hate my fridge, but that's another post.) As you need the herb throughout the winter, you can pull out what you need, zipper up the bag, and throw it back in the fridge.
Last year my lemon thyme lasted in the fridge until my herb garden started producing again. The mint and the basil only lasted about 6 weeks, but it's still better than nothing. I'm hoping for a good two months this year. Rosemary is also a hardy herb that will keep long periods of time. Don't even worry about trying to keep parsley for the winter. Parsley just doesn't keep longer than 2 weeks if you're lucky and it's cheap at the store anyway.
Happy harvesting, and enjoy your herbs without the hassle of pots on the window sill.