on my allotment, I started to create a couple of large new beds - digging up a large area of grass that was on my plot.
I only got 1/2 way through I have covered the undug bit with plastic to stay on top on the weeds and will just do little bits as and when I can. you might want to take a similar way. Its easy to get over awed by some jobs, so make it easy for your self and do little bits at a time.
Spring onions will work for you, as will little turnips.first time I have grown baby turnips and they are now a firm favourite. using in stir fries, curries or sauted
It might be worth trying some runner beans, You might only get a crop for a couple of weeks but normally everyone is sick of beans by the Autumn.
Dont forget all the chinese cabbages, etc they like growing at this time of year
see what veggie plants your garden centre has for sale, as plants at this stage will do much better. There hopefully is 8 to 12 weeks of summer growing left.
You've loads of space though, so you want to get some fruit in there now.
Raspberries, strawberries, rhubarb, currants, black berries etc, If you buy potted plants they will happily be planted now.
Remember that not everyone always has a great gardening year, we can all get dead buzy or be beaten by the weather, or loose whole rows of stuff to snails or pigeons. somethings work, somethings dont. Smile, have a glass of wine and think about what you might do next year.