Here are few of my environmental interests...
Environment Agency
I work for them in Flood Incident Management (formerly known as Flood Warning). I've just finished an assigment testing a new computer system that will help us to warn people better. Then I'll be training staff how to use it, along with all the other computer systems and things they need to know when on duty. Visit their web site to discover whether you live in a flood risk area and how to prepare for a flood if you are.
River Monitoring Project
Volunteers from all over Wiltshire measure various things at a spot of their choice. Monthly surveys include measuring depth and flow. Less frequent ones involve counting invertebrate and plant species. I got involved with the project during the summer holidays after I sat my A-Levels. I entered a lot of data onto the computers so they could analyse trends at the locations. My Mum is now a volunteer so occasionally I get to help her out when I'm visiting!
I wrote a web site for the project many years ago, but now it has its own site. So my pages are now gone (they were a bit out-of-date anyway).Go to the Wiltshire and Swindon Biological Records Centre and click on Recording Schemes.
Yorkshire Wildlife Trust
Slightly more relevant to this area. I have been a member for several years, but haven't yet joined any of their volunteer groups. Unfortunately most of their activities are more than a bus ride from where I live and usually happen on weekdays. Most of their volunteers are probably retired!