IT4Communities is the leading national IT volunteering programme. 
If your charity or not-for-profit or social enterprise would like specific IT help, then register with IT4C, and they could find a volunteer to meet your needs.
If you are an IT professional who would like to 'give something back' to your community, then register with IT4C to be matched with a suitable client.

IT4C can help both parties organise the project or task - from defining what the need is to an effective exit strategy. 

Worth a visit to www.it4communities.org.uk/it4c/about.jsp for more information.