This week, we’ve been on the look out for imaginative, engaging and comprehensive corporate sustainability websites in the UK.

Marks & Spencer, better known for selling the nation’s undies than innovative communications, surprises with a strong, attractive site. It kicks off with Plan A – the set of sustainability initiatives that has saved the business £50m to date.

M&S realises that its biggest impacts lie up and down its value chain rather than in-store, so its web-based communications reach out to customers. Users are invited to choose pledges that will reduce their own sustainability impacts such as joining the ‘Wash at 30’ campaign. Interactive features include a tally of the number of pledges made so far and friendly pop-ups of named contributors, together with their promises.

In contrast, some of the companies you’d expect to lead the way in digital media like Orange and Virgin, have surprisingly static web-based sustainability communications. BT is the best in this sector, offering a host of useful and easily downloadable material for initiatives such as its Skills Journey. But opportunities for the multi-channel conversations we’ve come to expect from the best sites are lacking.

No survey of British communications innovation would be complete without raising a glass to the power of humour, much appreciated at Innocent Drinks’ laugh-out-loud blog and on its twitter feed, followed by more than 23,000 people. Although not an out-and-out sustainability site, Innocent makes the connection between healthy products, happy employees and laughter – and manages to touch on many relevant issues without seeming to try. The corporate ethos extends to raising money for good causes with its Big Knit Campaign for Help the Aged and Age Concern. Customers are encouraged to knit funny hats for Smoothie bottles, and Innocent makes a donation for each one sent in. Knitters can upload pictures of their creations via twitter and flickr, and a ‘hat of the week’ is announced on the Innocent website. A handy ‘hatometer’ is available for uploading onto enthusiasts’ websites, giving their followers regular updates on the campaign’s progress. Lots of good ideas here for mainstream corporates.