Insects - nothing beats sitting in the garden surrounded by flowers with the birds singing and the sound of the bees hard at work. To encourage the bees to stick around why not buy yourself a bee nester. It's probably too late for them to use this year but next year will provide them a free home, meaning you build up a colony of these useful insects ready for Spring and Summer.
Other beneficial insects such as Ladybirds and Lacewings are good for controlling aphids so a bug box will give them somewhere to over winter meaning they are hand in your garden from the word go next year. The reason to do it now is so that the box is weathered in ready for when the temperature drops and they start looking for somewhere to hibernate.