Most of my garden mint goes one of three ways.
1. Make mint sauce, tend to do 2-3 jars each year, Chop in some corriander (around 1/5 the amount of mint), warm some vinagar (I prefer to use malt) throw in the herbs and gently simmer, add enough sugar to your own taste and bung in sterilized jars.
2. Freeze it in ice cubes, chop up very roughly and put in your ice cube tray fill with water and freeze, you can then either throw them straight in drinks to both chill and give mint flavours or use them like stock cubes for cooking.
3. Dry it for cooking, when drying the trick is to dry as fast as possible with all herb, they all have natural oils that are lost eith every second of evaporation of the water content. So the faster you dry the more oil you retain and thus more flavour. Handy trick I found is to use a microwave, the time varies depending on the herbs but just use stems with leaves on rather than mess about deleafing. Lay them in sparse layers no more than 3 layers high, stick your microwave on high for anywhere between 1-4 minutes checking them every 30 seconds or so and you end up with perfect crisp dry leaves. Be warned you have to sit and watch this until you get an idea of timings for different herbs things like sage can and will ignite within seconds of their total dry time.