Being a fan of bumblebees and the great work that I always knew they did for us I recently discovered
http://www.bumblebeeconservationtrust.co.uk/
These great little workers are in danger of disappearing. A little reading on this website and others will show you exactly what they do, the danger they are facing and the end result - should that happen - to us.
These happy little workers are more than happy bumbling around in your garden whilst you work there too. Find one in your house banging against the window trying to get out? Don't squish it thinking it might sting you but try and let it outside. If opening a window isn't the answer try carefully placing a plastic cup or glass over the top, slide something like an envelope between the container and the glass then take the bumblee outside. Bumblee will be happier and so will you.