London Cocktail Week returns this year, from 6th-12th October. As a week-long celebration of the culture of cocktails and all things mixed-drink related, it is a great introduction to the range of bars and bar people currently in London. One of the key features of the festival is the chance to get discounted signature cocktails at each of the participating venues, though you will need to buy a wristband in order to take part, and these can be ordered here.
The website alone is a great resource – worth checking for the cocktail bar tour maps, based on the 2013 festival week. A very handy way of planning an evening out, even if you are not available to make the week itself.