A quick way to do this is to use SharePoint Designer 2010. Open the site containing your list (your account must have appropriate level of access to update lists). Go to All Files then right click the list/library you want to update and select Rename. The Name Column (first) effects the URL, the Title column; the list name. Don’t forget, if you have any hard coded links anywhere, you must update those. If the List’s ‘Display this document library on the Quick Launch’ setting is on, then the Site Navigation will update automatically to point to the new URL.