Every allotment or smallholding owner needs a shed, and there are some great ideas in Stiles' classic Sheds book. One day I'll be building a studio based on a design in this book.
For general green ideas I have Dick Strawbridge's It's Not Easy Being Green book of the TV series, there are some useful ideas in here and more in the related blog. I also like Paul Waddington's 21st Century Smallholder for a no-nonsense approach to what is (and isn't) worth doing in an ordinary house.
Sarah Raven has written a great cookbook, which is wonderful for those "I've a handful of courgettes/basil/french beans and need a recipe" moments. I'm not so fond of her vegetable plot book, it has some good ideas for unusual things to grow but suffers a little from the fact that most of her readers won't have several acres of garden.
My vegetable growing bible is The Vegetable Garden Displayed from the RHS, first published in 1941 (I believe as part of the Dig for Victory movement). Terse, to the point and generally correct. Out of print it seems, grab a second hand copy if you can.
I also like a book found for 20p in a charity shop - The Good Life by Sally Gordon. Again this is out of print but it has some great stuff on setting up smallholdings and allotments, and a fantastic section on how to preserve fruit and veg (including charts on such things as exactly how long to blanch each vegetable before freezing). Great 1980's hair too. Highly recommended for practical advice.
A newer acquisition is a River Cottage manual (there are several, and they're popular) on preserves by Pam Corbin. Some nice ideas here such as preserving nasturtium seeds like pickled capers.
There's more of course, but a lot is still packed away - and like my friends I'm still searching for a good book on fruit tree pruning and grafting.