One of the best things i have purchased for my EUC rides has been this thing. On amazon they are around £10 but you can find them for £5 on ebay.
Being able to lift my arm up and take a peak behind me makes me a lot more confident when navigating around traffic. I normally have a big camping rucksack on and so cannot look completly behind me when riding.
Something worth considering as a stocking filler for Xmas i think ;-)