Hi guys
Will try not to go on too long about this - I work in environmental consultancy so could win an Olympic medal in wittering about this stuff , all of the ideas below are great and a fab place to start. The fact that you have a 'green' committee already means you are pretty much on the way, you'd be amazed how few organisations even consider such things at all!
In general the golden rule is to follow the mantra 'reduce, reuse, recycle' - so first look to reduce what you use (less paper, energy, water etc), then reuse stuff (i.e. proper cups instead of vending machine cups, or printing drafts on the back of once-printed paper) then finally using recycled materials. This is because even recycled materials have an impact due to the reprocessing and transportation of the material.
General excellent stuff about green offices www.green-office.org.uk/ - actually written for Scottish offices but relevant to all offices anywhere.
www.envirowise.gov.uk/page.aspx?o=gettingstarted for office waste issues, especially paper and consumables etc
www.carbontrust.co.uk/ for energy advice and tips including FREE energy survey and report!
www.bco.org.uk for general information relevant to the offices sector, they have a particularly good publications team and have recently done a report on setting up a Green Travel Plan. This is particularly important as if you add up the carbon impact of a typical office over its life, the carbon produced for energy for the building is actually about the same as the carbon produced by travelling to and from the building by the staff.
As you probably have already found out, there is so much info on the web you could spend your life researching this! Hope this helps you to narrow it down a bit anyway...
Good luck! Pxx